It's past midnight in the UK, so you're probably right. Most apps debut on Tuesday, when the App store also update their New and Noteworthy/Staff Favourites sections. I'm sure it'll make it to the front page, tomorrow.
I've never seen an app with a full 5 stars, one week after its debut, have you guys?
The SlingMedia app is just as popular (or "hot" given the rankings), but it's hovering in the 3 star range because of the lack of 3G. There's always SOMETHING that will make people grade an app down, so Peggle's great reputation is well-earned.