I've had this plug for a while as part of a Waves bundle and I have to say I've shied away from using it because for some reason the thought of it sounded "artificial" or as if it were "cheating." But today I've been having some real trouble with a bass sitting in the mix and Maxxbass really was the answer. 
 
It's a Trilian electric bass that's got a little overdriven Mark Studio mixed into it, and it was sounding fantastic on its own...real gritty in a kind of early Joe Jackson kind of way. The bass line is fast moving and quite intricate and I really wanted every note to stand out without swamping the rest of the mix - the trouble is, it clashed with a punchy Pianet sound in the upper mids and I just couldn't get the two to play nicely together. Tried all kinds of EQ and compression strategies and it just seemed like I couldn't have my cake and eat it. At the last minute I slapped Maxxbass on the bass bus, cranked up the Maxxbass element at the default settings and there you have it! The two sitting together nicely with excellent clarity and punch. The Pianet was no longer drowning out the gritty frequencies of the bass and I could hear them without cranking the bass so much that it drowned out the Pianet. Really happy with this plug (in this case anyway) although I could see how it could be overused!

All the time. It's great for separating bass and kick frequencies by pushing the bass harmonics up. I also use it during final mixdown when I want to feel the kick. Recently, I've been using Renaissance Bass instead of Maxbass. Same concept, but it is a bit more musical.
 
Regards,
Dan

MaxxBass works.
 
You should probably have a system that reproduces full range bass so you can hear what it is doing.
 
If you use it to make a small system thump... you may end up with some craziness on a system that can actually produce bass.
 
It is best if you use it on a full range system to tweak the playback so it can also sound good on a system that needs the bass to be tweaked.
 
If that makes sense.
 
best regards,
mike

I use it a lot.  It does wonders for my backing tracks for my live gig.

dcumpian
Recently, I've been using Renaissance Bass instead of Maxbass. Same concept, but it is a bit more musical.

 
Isn't Renaissance Bass just a simpler/cheaper version of MaxxBass...?

No, Ren is a re-developed second generation of MaxxBass with a simpler interface. I prefer it over Maxx too.

carl
No, Ren is a re-developed second generation of MaxxBass with a simpler interface. I prefer it over Maxx too.

Thanks. Since Ren is half the price of Maxx I thought what I posted. Weird that a newer version is so much cheaper...

I started to use it to punch up some bass frequencies, but to the detriment of a larger sound system. In other words, it helps make bass more present and punchy on smaller systems, but it muddies it up on really good audiophile systems, in my experience. So, I stopped using MaxxBass, personally.

You have to:
 
a) Find the right frequency. This can take a lot of experimentation, depending on the material.
 
b) Use it in moderation. Very important.
 
Regards,
Dan
 

I used to use it abut a decade ago when i dabbled in pirated software.  I even used it it separate my kick from synth bass for project I won a contest with.  Needless to say I decided to chuck any pirated software a decade ago and thus no longer use it.  I do recall it gave great results.