I use this tiny amplifier at home for practicing with an acoustic or electric guitar, with another instrument (other person playing bass guitar) and for writing music. I would not think it could be used in the practice room because of the low wattage.
Volume is enough and the controls are just enough, although it overdrives a bit if you want a bit more volume, as gain control has to be adjusted higher in order to get more volume.
I thing it is a great advantage this amp can be used with 9V battery or pluged into the wall.
One disavantage is the sound is quite like a "radio" kind of sound because the small size; but it can be an advantage if you like that effect. The only comparison I can provide in the same category is with the Marshall MS-2 mini amp, and Orange one sound better.
I once enjoyed the combination of this little amp with an acoustic guitar, as you can mix the acoustic sound of the guitar with the amp signal and even use effects, like tremolo and reverb.
Overall this amp is very well constructed and usefull if you need your guitar to sound to practice or have fun.