Ive used the 2 channel and the 4 channel ones, not bad mixers at all. I personaly didnt like how the headphone cue works (its on a small fader if i remember rightly), just personal prefrence though. Effects are nice, but it seems to me like more thoughts been put into them than the rest of the mixer. The different EQ settings are quite cool, never had enough time to check them all out seperately though,
Definately a try before you buy one I'd say, but nothing majorly wrong with it in my experience.
EDIT: The cues selections only on a fader on the 2 channel mixer, so no worries about that if your looking at the 4.