The apps still won't run in the background, but yes, that's the intended purpose. Basically, take an IM client as a great example. For most of them out there (Beejive and others excepted, because they're smart), when the app isn't running, you're logged out of the service, and people have to know your phone number to send you messages. With 3.0, apps like IM clients can notify the phone directly when its user has received a new message, then they can tap into the app and get said message. This is how it was initially intended to be, and it'll be nice to finally see some follow-through.