My husband was reading another reason for the usernames you cant pick yourself... everything you get ebook wise will have watermarks with your user name. so if you get caught selling it you're screwed.
I got in yesterday. Site looks great but I don't enjoy it very much, you never know when you are finished on a page. It just let you search and search even if there's nothing to find. But considering what it's like, I do like the extra story behind it all. But shaping the experience is only by leaving a comment on every page. So you can only suggest things instead of creating.
I know a couple of people who are in, and they have declared it to be rather boring after the initial excitement of seeing it all. And some "Dueling Wizards" something that hasn't worked in over a week.
I think the fans are going to enjoy the new content by JKR and getting the electronic books, but I think the site itself is going to fall way short of what fans expected and even shorter of what they want/ed--to "attend" an interactive virtual Hogwarts.
Shylaah