Well, after reading this article and a few others tonight...it's become clear that some of my wish list points are not possible under the terms of Apple's SDK agreement, no 3rd party apps are allowed to run in the background. This means that my #1 feature is impossible, and it kinda puts a damper on some of the others (like for example, opening Safari to look at artist info and things like that isn't nearly so enticing if it means my music has to be put on hold till I come back). Sadly, it looks like I'll have to rely on my own music collection if I want to listen to music while web browsing... This really sucks since I'm still waiting on them to release PwnageTool 2.0 so I can transfer my songs over (Linux user...no iTunes).
As another note, although I still wish they could work out a deal to pool their data ;) ...Last.fm now has an app too. I really like those guys, they seem much more open source friendly and focused on community/user generated content...but I never seem to enjoy the stations Last.fm creates as much as I do my Pandora ones. Still, the Last.fm app seems to be a bit more featureful, including a few of the ones on my list...however their caching/lag problem is even worse than Pandora's!
So anyway, as it stands...my custom radio stations will have to be saved for music only times as far as my iPhone is concerned :/
[Listening to my Pandora station: "Igneous Radio" as I type this...isn't multitasking wonderful]