The good things
The sound quality and flexibility is great. The sound is very similar to my ancient Mackie CR1604:s, which I still use two of for studio mixing. It seems extremely sturdy built, unless you drop it with knob-side down.
The annoying things
A minor thing is that the HP filter on the channels is at 100 Hz. That is too high. It should be 70 Hz. The graphic equalizer seems crafted to solve problems that may occur in a live situation by surgically cutting some frequencies. It is completely useless for anything else. It's impossible to sculpt a sound cause the frequency curve will have isolated pikes and sound pretty weird. One selling point for this kind of a mixer is that the effects section has a decent reverb. You can just hook up and rehearse or submix on stage without jacking in an external effect. Unfortunately the "running man" 32 bit effects suck. It's virtually unusable. And what's the purpose with delay if there aren't more variations in delay time? The usb interface "sings" when connected to my HP Pro laptop. Digital noise almost forming an erie chord. It probably works with some laptops. This problem is common for usb interfaces built in in mixers from many brands. I have to use a Tascam US-122 MK II interface anyway since I need midi too.
Well, if I hook up my little effects rack, using the TC M300 "TC Classic Reverb" and Behringer FBQ1502 equalizer I get happy rehearsing. The street pricing of ProFX12 is recently lowered to a point that the annoying things are just a little annoying. I wouldn't hesitate using this mixer for serious recording.
My phone camera is incredibly crappy.