Just picked up a Little Smasher for my home studio guitar work and figured I'd see how my basses sounded through it. Without a doubt, this thing is voiced for guitar. Feeding my Zoom B3 into the little amp got me closer to bass-type tones but it sounds to me like they put in a high-pass filter of some kind to maximize the 5 watts for the guitar spectrum as the frequencies below ~200Hz do not seem to even exist. This would make sense for its intended purpose but I cannot recommend this little wonder for bass use.
Makes a neat little guitar amp, tho! It does tend to go to grit fairly early on the 'gain' dial, so use judiciously. The gain itself is very Marshall-sounding to my ear and the bass/treble knobs provide huge amounts of boost/cut. I'm using it with my 2X10 custom-built bass cabinet and am pretty pleased with what I can do when the right effects are in front of the amp itself. As stated in various reviews the 5 watts available in the guitar spectrum get quite loud, again most likely due to some clever spectrum filtering.