i'm a little late to this thread......i use my VTB-1 for both guitar and bass DI. it does an 'ok' job at both. if i had a sansamp, i wouldn't use it. but it DOES get a nice trebly (midrangey) growl to it that really helps the bass punch through the mix. i usually stick the toob around 10:00 and it's plenty.
of course, part of that is my bass--a late 80's yamaha that has plenty of midrange but no real bottom end to speak of. it really sounds a lot more like a ric4001 than a fender bass. this thing couldn't rumble if it were provoked......but it certainly has plenty of punch.
anyway, the mating of that bass and he VTB-1 works plenty well in my situation. lots of folks poo-poo it as a bass DI, but i found it does fine with my bass. with a couple fender basses that i've used, though, i'd certainly prefer something else.
cheers,
wade