Let the hive mind of Engadget get that for you.
"I'm in the market for a new phone and money isn't a limitation. I'm also not partial to any particular US carrier, but here are some of the features I'd like to have: WiFi, GPS, good coverage in lots of places, push Gmail (a must!), physical keyboard (a must!), a touchscreen, decent battery life and a relatively slim body. And please, nothing that has a fruit logo on it. No offense to the fruit fans, though. Thanks!"
Are we talking true multi-tasking where both apps remain open or a service that calls the other app and closes down one app on completion of the service to save battery life? There's a big difference IMHO. Plus, can anyone whose dug deeply into the iPhone SDK say if the latter can't be done - also a big issue.