Since I got the SansAmp about 8 years ago, I don't do a lick of bass recording in my studio without going through it....although most think of it more for drive and attack, it can also really ballz-up the bass frequencies if you're going for a more fat, subdued, classic sound.
I agree with crgaston, too: it can make an already aggressive bass sound (like with my Ric or SCSD) transform into a hungry lycanthropic Uruk'hai!