I bought two of these as a replacement for an older, heavier passive PA system I was using. I'm a solo acoustic performer with a pretty simple setup and am really happy with this product - I've been using them for just over a year solidly and they've been faultless so far.
Sound quality is good, I gave this a 4/5 based on the price of the product and the clarity/warmth of the sound. The high end is a little harsh at times but the basic in-built EQ is useful if you need to tone it down a little. The low end response is surprisingly decent - I plug an electroacoustic guitar and a vocal mic into these and there's plenty of low end for what I need. I've heard better sound quality from much more expensive active PA speakers, but I've also heard MUCH worse quality from similarly priced speakers - so I'd say these represent excellent value for money, as does most Behringer kit that I've used.
Power-wise, these speakers have suited every situation I've needed them for so far. Powerful enough to use outside or in larger venues, but still good at lower volumes also. A great all-rounder. Also, they're not too heavy and pretty easy to transport.
A quick note on the in-built preamps: You'll want to use a separate mixing desk to get some more control over levels, EQ, fx etc. However saying that, I have plugged an instrument and a mic directly into the speaker on occasion, and honestly the sound quality is more than decent and very useable. A simple in-built reverb would've been the icing on the cake, but you can't have everything!
Overall - very impressive for the price and definitely recommended.