"My bass is too sinewavy, I can't hear it when testinng mixdown on set of cheaper speakers and have no money for crazy expansive Waves bass enhancers!" ...if you reckognize yourself in this statement a bit, you'll like this plug.
Obviously as Waves plugins are iLocked, I wasn't able to demo and A/B it, but from YT videos and stuff XBass can be used in pretty similar manner. It's not exactly the same. XBass saturation adds a bit more of higher harmonics then just 1st and 2nd as Waves enhancers do (I think). That could be good or bad thing depending on material, so no point in judging that. When you turn "Soft enhance" knob, in low values it nicely soften the bass area. In higher values it punches it up pretty hard. Watch out though, when fatiqued, you can mudd your mix by that in a second.
I find it great when something needs some more bass care. You shouldn't get fooled by volume. Sometimes all you need is good EQing, but sometimes it's not right no metter what magic you do on EQ. Then this plug comes really handy. And for that price...
Bad side is GUI. Knobs lacks range descriptions, but I would like to be helpful and becouse developers are Slovaks and Czech and Slovak languages are almost the same, I contacted them and asked. So that frequency button: Low value is 50 Hz, value of 5 is 200Hz and value of 10 is 1kHz. :)
Summary: It's pretty cool plug. I guess Waves plugins are more quick to use and pleasant to have, but if on budget, this gadget can do lot's of things in similiar way. Amazing for weaker basses or kicks when used gently.