It's actually a homescreen replacement, and some sort of fancy pants lock screen. I don't know if I would enjoy having my lockscreen covered with all the pictures of dirty jokes my 70 year old aunt likes to post... They're also bundling in a few apps for chatting and sms.
Sounds like a much better move than trying to come out with their own phone or trying to fork Android. This will be accessible to a lot more people. I don't see myself going near it though. There's just too many potential privacy issues. I'm guessing most people won't care about that, so this could be big for them.
