Last night was my first gig since getting MF3, which is a bit poor since I got the advanced version...
Despite using the DL now for well over 2 years I was a bit nervous at this outing as accessing various bits of functionality are different to the ways I have been used to. Thankfully, I had spent time getting accustom to things in a static environment and it meant when show time hit, it wasn't as painful as it could have been. Thus I would recommend new users spend plenty of time pre-gig getting familiar. I also think it looks more impressive now than it did before, the previous incarnations did look a bit Fisher Price, but this one looks professional and a bit more technical. Good for impressing audience members :-)
As other people have noted, there is a bit more lag in this version, especially on an iPad 2, I'm guessing due to the greater level of control and functionality to be loaded. However, this seemed to get better with a few minutes of use and working through all the menus, it was like it then buffered the features. Overall, it worked fine and the slight delays thankfully don't impact operational performance.
I can read the numbers on the scale, just, but to be honest I typically rely on the box at the top and their general position relative to other faders. So not sure if this is a problem or not, your mileage may vary.
I got to like the new mute and view assigns especially the multi select as this gives you a load more options, rather than having to repeat the settings in each view.
Having the access to a masters page was also really nice, a much quicker way to get things under control should you have feedback issues or someone complaining they can't hear their monitor when you are running 4 or 5.
On MF2 I used to get the resync on wifi a few times a gig and the occasional stutter. With MF3 it would appear to be a lot more stable in the connection and no re-syncs were experienced.
I haven't used some of the new features such as the VCAs (DCAs) or groups, maybe next time :-)
So, in summary: If you are waiting to upgrade, stop waiting and get it done, it is a gem of an upgrade and definitely keeps the DL fresh.