I bought one of these in one of the PA packages Thomann do and was very impressed with it. I play in a heavy rock band and pair this with Behringer Eurolive speakers using two channels for the mains and two for the fold back.
We've played some quite large venues and this has given us plenty of headroom. We have two guitars, a bass, three vocals and drums going through it and it handles the sound with perfect clarity. The bass response is superb and yet never detracts from the rest of the range. Even the bass drum doesn't cause any issues with the sound.
I run it at full volume on all channels with the volume levels being set by the desk. I have never run up to clipping level but have been close and so far there has been no distortion just lots of volume!
I like the fact that each channel has both male and female XLR sockets and the only downside is that it is very heavy.
The four amps can be bridged into two very powerful ones if required but I can't imagine ever needing that sort of power in the venues that we play and I've never had the speakers to take it so I've not tried that mode yet.
All in all I can wholeheartedly recommend this amplifier, it has bags of power and a great sound and feels like a quality product in every respect. In fact I liked it so much that this review is for my second one! Our band is so reliant on it that I bought another one just in case the worst should happen on stage and I can just swap the leads onto the spare but in reality I very much doubt that the original will fail. Not for a good while anyway.