The songs aren’t greyed out, right? The database has some songs that aren’t available in your area. If you try to play these, it ignores the request.
Not that I’ve noticed, but I will double-check.
Got my invite this morning. Spent about 20 minutes messing around with it on my home computer, which I rarely use because I have an iPad. Downloaded it for my work computer, but the firewall blocks it. Which is strange, because it doesn’t block Pandora or iTunes at all, and people use both of those all the time. This puts a damper on my ability to enjoy the service–I planned on using it more at work and in the car than I would at home, and now work is not an option.
I do have a bunch of stuff on my iPhone now, though. I’ll have to play with it some more tonight.