Maybe I'm the only one but fast app switching would be what I want for IM's. I use Trillian, and sure it works great with iOS4, but its annoying having to wait for it to re-connect to the server every time before I can read the messages I already have on the phone. Even if it just suspended and picked up where it was, but then had to wait the 10 seconds to connect to the server in the background before sending a reply message would be great. I hate having to leave the app to do something else, only to get a message 10 seconds later and having to wait the 15-20 seconds for it to get by the "resuming..." screen.