I've been using Izotope Ozone 4 for years and used it to master 5 albums.  I really liked the presets but...  well, they don't make it anymore and there's no support for it.  I'm not really interested in spending $250 for Ozone 7.
 
Is there anything else comparable?  Maybe something that won't set me back several hundred bucks or something with more features?
 

Ozone 4 still runs, is 64 bit and doesn't really need "support" -- if you are happy with it, stick with it.  If there is something specific you want/need there is no reason to toss Ozone 4, just find a stand alone plugin that does that new thing.  I have Ozone 4, 5, 6, and 7 all installed and working inside Sonar but I still often use other plugins (T-Racks, Waves) depending on things.

It works, but I'm complacent with v4. 
The albums I used it for sound good, but I'm looking for something to get "great" results.
 

What's wrong with Sonar? Also depends what you consider Mastering.

For some it's getting the files ready for finalising to a medium for sale. Eg getting ready for Redbook CD release.

For others mastering is the process of final eq, and dynamics control to maximise levels add meta data etc/

EverSoul
Is there anything else comparable?  Maybe something that won't set me back several hundred bucks or something with more features?

In short, no. 
 
Although there are many inexpensive limiters that are quite capable, none are better than Ozone 4's Maximizer. You'll have to spend over a hundred bucks just to get something else that's in the same league but not necessarily better. FabFilter Pro-L, for example, beats it, but it's 200 bucks.
 
Honestly, given your comfort level with Ozone 4, Ozone 7 is probably your best bet to ratchet up your quality (yes, it really does beat the pants off of O4) with a minimal learning curve.
 
 
 

Must agree 100% with Bit - Ozone 7 is a massive improvement over version 5, which I was using - and very little learning curve
Nigel
 

It sounds like you're an experienced mixer.  You should probably heed Bit's advice, but I did notice that IK Multimedia's Stealth Limiter is on sale for about $64 right now....http://www.ikmultimedia.com/news/news.php?id=626
 
Maybe all you need is a Maximizer to add to Sonar's suite of plugins?  You may save yourself some cash.
 
I know this art is way more about ability and knowledge and way less about the latest plugins, but I've blown some bucks in the process of gaining that knowledge and expanding my abilities:)
 
I started with T-RackS, then Ozone 5, but I've since moved toward mastering with plugins and not suites.
 
If you're considering that option, I'd suggest IK's Master EQ 432,  IK's Bus Compressor, and the Waves L2.  But, the Sonitus MB and the EQ's bundled in Sonar may do the job too....

I too enjoy using ik multimedia, especially the EQ 432. I move back and forth with compressors/ limiters depending on the kind of transparency I need or how "chewy" I want the low end to be. After hearing how good the 432 works for overall tone shaping, I have had my eye on their Stealth limiter. They really have a few gems in their lineup.Flavor of the week? Classic Limiter. It's kind of hidden in their classic collection and has a lot of the best of multiband and "old school" response. Anyway, they often have "mega sales"where you can get awhole bunch of good plugs on the cheap. Can't speak to Ozone, but can't say I've ever heard anything but good things, and if you are familiar with their layout, that has to weigh in  considerably in your decision

Thanks for the input guys.  Since most people still pointed to the Ozone, I gave a trial run to the newer versions.
 
I'm sure 7 is better, but I really like 5.  Its enough familiarity to feel like an old glove and it looks like there's some minor improvements over what I was using as well.
 
My brother uses Ozone 3 (for the wideners only) and T Racks - didn't much care for that though, but him and I work with completely different genres of music.
 

IK's Stealth is FRIGGIN AMAZING...and THAT'S A KILLER DEAL... I have virtually all their plugs and this is on every mix/the others aren't...
 
Fab's bundles/individuals all have 30 day trials... I find them to be the most visually intuitive, easiest to use, low on cpu... and prestine... widely regarded as top tier everywhere... I have most of them and use them the most.
 
Ozone/suit... Got it... learning it... but FF still has me by a wide margin for most things...
 
A couple hundred others are taking up disk space...