I've been thinking about this for a while now.
 
I looked at LANDR and whilst my mixes are not quite as loud as their's, it just seems their algorithm is about turning a -20dB LUFS to -10dB LUFS in one fowl swoop. There doesn't seem to be control over how much stereo width or style of dynamics. So my guess this is aimed at people looking for quick masters or people who don't know much about the process. I mean how do we know it's not a tealady who just happens to be proficient with Izotope Ozone. Joking....sort of.
 
Cloudbounce was something I discovered which is the same idea as above however they offer a pay as you go service as well as mastering options. A 320K MP3 and 24-bit 44.1Khz version for a small fee just less of $5. They also have subscription options.
 
Abbey Road offer online mastering for a bigger fee however if you have the budget then this may be the difference between a radio hit and internet damp squid. 
 
So I was thinking Cloudbounce because the pricing is fair and it made a really old badly mixed track I did, sound almost listenable. Just think what a 24-bit version could be like.
 
Then there's a quandary, I have all these assorted plug-ins that can be used for mastering and detailed mixing. In a better environment and a bit less erroneous mix decisions I could do a better job. My newer master versions are not only louder but have more definition. 
 
It does beg the question though, should I spent hundreds of $ (£) on plug-ins that are only used to shape the sound until somebody with proper analogue gear and a phase-free environment is able make it sound compatible in all situations. I enjoy the challenge and slowly finding myself wanting using to Analogue emulation or the proper equpment in place of software plug-ins.
 

Nothing compares to learning about mastering and how to master and setting all these things for yourself.  Not using factory presets in the software either.  Starting from scratch and setting everything according to the track and how it sounds.  Provided you can do so.  Hardware and software will also get you there.  It is all about using the right tools well and making good choices.  This is all better to me than sending something off and just having an automated process applied.  I think you need some fine tuning input instead. Things like listening to amazing references and switching back to your track.  Comparing all the tracks in a CD for texture and sound etc.. You have to do that.
 
I have used some fine hardware for mastering.  EQ's costing $5000 and the best stereo outboard compressors and limiters.  These things have slowly moved inside the digital realm and many mastering engineers are not shy about using software to do the job. There is some incredible stuff out there now.  More, and what that means is you can alter your mastering chain now more diversely.
 
I have mastered some albums and bought some tools and I am happy I did.  Things like PSP Xenon for limiting and some really nice EQ's and compressors.  C2 type or API2500 or Neve multi band etc..  Things with character and some mojo.  Others transparent and accurate.  Consoles and tape and entered the realm again too.  They can be included in the mastering chain easily. They can pay for themselves too. 

interpolated
...how do we know it's not a tealady who just happens to be proficient with Izotope Ozone. 
 

It's not even that. It's an automated process.
 
Still, they do a surprisingly good job considering it's an algorithm. You could do at least as well with practice, and have a lot more fun in the process.

I think that learning how to master makes one a better mixer because it becomes much clearer how much better a mix can be if it is good before mastering. Trying to kick the can down the road by "fixing it in the mix" or "the master will be better" hardly ever makes a track stand out.
 
Now, I'm certainly not suggesting that we can all become excellent mastering engineers, but understanding the process and being able to use those techniques helps all around.
 
Regards,
Dan

You'll never learn to drive as long as you use a chauffeur.  Personally, I would not use an outside service because I would like to grow in that ability myself.  However, it can come in handy for comparison.  I recently watched a video from Jason Moss comparing mastering via a mastering engineer vs LANDR.  It is very interesting.  Just keep in mind, the mix is professional to begin with.  Here is the link.
 
http://behindthespeakers.com/landr-mastering/
 

Is there a half-decent studio nearby?
I paid a pro to mix/master my last album, and learned a lot by sitting and watching/listening.  It cost more than an online service, but it was an education (as well as getting a product that will hold up against anything else similar on the market).

I should probably clarify my point on not using an outside service.  I, like most others here on the forum are increasing in knowledge and ability in all aspects of recording, including mastering.  If my project was professionally recorded then I would use a professional mastering service, i.e. an actual mastering engineer.  But as long as I'm still learning, I want to find out what makes "That sound".

We had a blind listening test here awhile back using the same mix mastered in Landr, someone on the Cakewalk team using Sonar, and a professional mastering studio.
 
We had a vote on the results. It was amazing to me the difference in personal preferences . I thought I could tell which one was mastered in the pro studio. I was correct, however it wasn't a night and day kind of difference. They all sounded good. It was a split on which ones sounded the best.
 
I think we can do as well or better than LANDR or any of the other automatic mastering houses. LANDR doesn't know what your personal preferences in a master are.
 
A few things that helped me were reading this forum and looking at mastering chains the pros use. Even if I use a different plugin and duplicate something they did in hardware with software those chains can be really helpful. Once you figure that out , you'll need to understand each plugin and use it to the fullest potential for your application.
Sometimes a minimalist approach is better than adding a bunch of plugins. The mix might need more subtraction than addition.You won't need everything for every mix. 
Programs like Ozone and TRacks can be great tools, but I seldom use the presets exactly as they are.
One thing I love about Ozone 7 is it allows you to put any plug in into it and demos in mp3 mode. This is really helpful, since pretty much everything ends up as AAC or Mp3 online.
 

I don't really care about the lossless market because I feel this has cheapened the whole process. What's the point of fancy masters and such, if they are being diluted and replaced with psycho-acoustic placeholders. OK for streaming I suppose however not as a master offline copy.
 
It's not like I don't have the right tools for the job. Maximisers, Limiters, Studer Tape Emulations etc. It's just I know I don't have the right acoustics, compensation, room environment/calibration. So rather than kid myself I rather get someone or even an algorithm to do it whilst I don't.
 
Recently I started reproducing older tracks from the clips and stems I still have. Occasionally creating new ones and variations. It's just so the final product can be a CD quality download from somewhere. I want to ensure the final mixes are better than I am capable of.
 

You can get around some minor acoustics issues with monitor correction software, and/or a little studio treatment. I personally like to get into my own mastering.
 
I understand it isn't for everyone.There is a bit of education involved and some of it is ongoing.Some people just don't have the time to do all of it.
 
LANDR or similar will be better than trying to master it if you feel ill equipped. The nice thing about daws though is we can make as many copies as our hard drives will allow. IOW we can afford to experiment.
 
There are also those "special sauce" plug ins like the most recent from IK and the ones by Waves.They don't tell you what happens under the hood, but they can be helpful. The presets in Ozone are sometimes what those without much experience use and they can be decent all depending. 
 
It's nice to have options available.
 
If you have a bad monitoring setup though, it can be tough to recognize a good master when you hear it.