I needed a loudish amp to gig with, through which I could also put my guitar synth, which really needs a flat input to bypass guitar eq, FX etc... The Behringer GMX-212 was the only one I could find, and it does the job well. However, I use my Line6 POD into one pair of inputs at the back, because I don't yet think £100 for a floorboard to access FX, wah, and have a decent number of presets, is justifiable, so I really only use it as a power amp/speaker combination.

My biggest gripe (AND IT IS A BIG ONE) is the quality of the design and build. The knobs all protrude a good inch from the top lip of the cabinet, which makes them vulnerable to being knocked. And, when knocked, as I discovered, they broke off easily, revealing themselves to be moulded plastic with no metal shaft (therefore irreplaceable without taking the whole thing apart!). I actually didn't know how they came to be knocked off (I suspect my 2 young kids), but when I contacted Behringer they were amazingly snooty, commenting that I wouldn't expect Mesa Boogie to replace something I had damaged myself, to which of course I replied, I wouldn't expect Mesa Boogie gear to break so easily!
They were very unhelpful when I pointed out this was a serious design flaw, and they refused to acknowledge there was a problem at their end.