We dragged our feet upgrading, after we took a beating going from 8930 --> 8965 and had to revert back to 8930.  This weekend we took 9035 because of all the MAPI fixes we've been waiting for, and it seems stable.  We have a large MAPI userbase, and we haven't had a single complaint in 3 days, so that is good news.

Only complaint, more like "something we've noticed", is administrative.  Our monitoring graphs show a noticeable increase in CPU usage now... in the 2x-3x range compared to 8930.  It's still significantly lower than it was on the pre-CORE versions last year, but it's hard to ignore double/triple CPU on 9035 vs 8930.

Is there some kind of multi-day conversion process running in the background that our admin team hasn't spotted, or is this the new normal?  This is against an (approx) 8.5 TB mail store for just over 2,000 mailboxes.