Marco Arment on Apple’s Geniuses and killing apps in the multitasking tray:
I don’t know why Apple hasn’t yet explicitly told all retail employees that “killing apps” in the multitasking tray is unnecessary, unlikely to solve any problem, and actually unlikely to have any effect at all due to the way iOS multitasks.
I haven’t heard a Genius tell me this but I know this has an effect. There is some condition on my phone where email won’t download; no push notifications (I use iCloud) no interval downloads. If I launch the Mail.app, it will check the server and download new messages. But killing apps running in the background always solves this problem and suddenly my mail will start to download in the background and push for new messages starts working – even without launching the Mail.app.
I know killing apps shouldn’t have any affect on the way iOS multitasks but, for me, it does.
And, yes, I’ve restored the phone from scratch as if it were a brand new phone.