I think Apple has decided they don't like multitasking on its merits. You can only do one thing at a time, so why run more than one application?

Instead, they're putting their effort into making application launch and exit very fast, and cautioning developers that they should save all important state, and restore it all next time.

I was wondering if it would work creating a second type of app, a Service, that has no gui and only runs in the background. They'd have an api that allows them to communicate with a regular app. This way, something like Pandora could be split in two, with the background service running constantly, but the gui closing as usual.

This make it easier to manage background tasks, and also eliminate the problem of users leaving all their apps running. I guess if the makers of a Service decided to make their api public, other people could develop alternate front ends for it as well.

Probably none. Multi-task, if it comes, will come on the iPhone and iPad at the same time. They either aren't ready to figure out how it fits into the OS model, or they've decided it shouldn't for now.

I think so, too. If you think about what is making Android devices run so slow, it's almost always some misbehaving background services. Unless there isn't some smarter way controlling the scheduling of foreground applications, there won't be multitasking and fast speed at the same time with a comparable CPU.