It's an okay little device for practicing your bass on the go. However, do not except anything spectacular.
I bought this amp couple of years ago to practice my bass with headphones at home, but quickly switched to an audio interface at home, because of the sound quality. So now i use Vox when traveling and i can't bring anything better with me.
I ran that amp with different headphones - Sony MDR-7506, Audio-Technica ATH-M50X, couple of random earplugs. The best results so far were with ATH-M50X, Sony's expose all the hiss and aren't really usable with Vox. It's probably because this little device is just not able to drive Sony's (64? ohms). So the right headphones are critical with this amp.
Featurewise, i basically use the most plain settings - no overdrive, a bit of gain and bit of tone. Rhythm section is a fixed list and with no way to set the tempo. So pretty useless. However, you can compensate that with your phone, rhythm app and aux in.
Overall, it's okay to have it, but if you're looking for better sound and mobility, check out Phil Jone's Bighead.