I have a 3GS and ever since I updated to iOS5 I have had problems with performance in mail.app. It has generally been extremely slow but the main issue is that every 3rd or 4th launch, it tries to connect to my mailboxes (two exchange mailboxes - one for work and one gmail) and gets stuck at "Checking for mail...". I can leave it for 10 mins more and nothing changes. If I kill mail.app and restart, it is then able to connect fine. Today I got a 4S and having restored from my 3GS' iCloud backup, I am having the same issue. Has anyone else come across this?