1. No issues with performance at all. Loaded up a few heavy projects in each DAW and everything sounds OK. No glitches in playback or anything like that (except for Logic's "first run through" stutters

2. The 828 MK3 photos on the MOTU website aren't true to the actual unit. It comes with rack ears and square edge profile on the front corners like the Ultralite. They must have photoshopped the corners out for the front photos to make it look curvy and modern.

3. CueMix works as described and the EQ / compressor sound quite nice.
4. Outputs are very, very hot. Even with my monitors turned all the way down to 0.5 on their scale, I need the 828 output to be way down at -34dB to achieve comfortable listening volumes. This means that none of the meters (on the unit itself or in Cuemix) are of much use - they barely register the signal. I might be doing something wrong but I can's see any way to attenuate the output and still get some accurate reflection of what's happening at the main outputs. Even though I had the output turned considerably far down the scale when I started testing it, I still managed to get a sudden loud blast which I think has fried my Rubicon ribbons. Damn.
5. No bus power which is a bit of a shame.
6. Miniscule knobs which are too close together, just like the Ultralite. For something they are also marketing for use as a stand alone mixer, it's a fiddly set up to use from the front panel.
7. The meters on the front don't seem particularly accurate with regards to timing. E.g., if I set up a drum loop with a kick every quarter note and playback the loop, it's bang on the beat initially then on the third or fourth flash / beat, the front meter of the 828 will be slightly delayed, then it skips back into flashing in time again, then another delay a few beats later. Strange.
8. I'm puzzled why there is no integrated panel for Cuemix or 828 audio options in DP. Apogee does it with Logic so why can't MOTU integrate their own hardware config panels into their own sequencer? Unless of course it's going to be in DP6.
Overall, I'm quite impressed. Doesn't sound better than my Duet did but it has all the I/O I'm likely to need any time soon.
Recommended (but doesn't trounce the cheaper, smaller, bus powered Ultralite if you ignore / don't need any of the Cuemix stuff).
IMHO.

David