Heh, an interesting and original start to the story that quite catches the reader's attention. I think this is going to be quite a defining summer for Harry & Hermione and I daresay Harry's going to get some extra, muggle, backup out of it before he returns to Hogwarts. Meanwhile, it should be rather colorful to watch the meltdowns with the Order and the Weasleys when they realize that both he and Hermione are gone, and gone muggle to where they can't be easily tracked by magic.
I thought the introduction of the gang was nicely handled and I loved that one's thought about just who/what whould be big and bad enough to scare Harry.
There're a few typos here and there (I caught at least one homonym problem) but it's an excellent start on a story with an original premise.