I am using it with Gmail over IMAP, and i have seen 2, 3 and 4.

The 100% I can sort of cope with (many apps *briefly* spike the CPU), but it is annoying when listening to podcasts as it causes them to "stutter"

On a number of occasions I have seen items not getting marked as read (although that might be as I leave email on 30 minute updates).

The search thing is very anoying, but luckily I can just fire up a browser and serch via that