40 watts is, quite simply, a lot of power; I've never been able to set the volume to this thing above 6 without fear of deafening myself.
Build quality is 4/5 , as plugging anything in to the dedicated AUX IN port for backing track play results in horrible buzzing and insanely loud popping noises. This was tested across several different aux cables and portable devices.
Other than that, the amp itself is very solidly built, and can definitely take a few knocks. The overdrive channel feature is a bit rubbish, but the clean channel is great. EQ controls are good.
Another note : This is very useful to bring to parties as a speaker. Simply make sure you're set to the clean channel, set the volume low (1 or 2 out of 10), and use an adapter to connect the 3.5mm jack from your phone to the regular guitar input jack. Many friends have commented on how great the sound is playing back party playlists, and the best part is that you can go from listening to music to playing it, with just an electric guitar and an aux, with the same amp. Very versatile.