The iWFMS and more

Today's iPhone update added two and a half big features, in my opinion.

The double-click preference is huge. I went for a walk after updating my iPhone and I used it constantly.

The double-spacebar trick is simple and cute.

The iTunes WiFI Music Store Store on iPhone (say 3x fast) is pretty neat - it loads quickly, searching is very simple (but informative) and it does what it should, and no more. I have one question, though. The following happened when I docked my iPhone after purchasing a track on it

1. The purchased song was copied to the computer
2. iPhone synced its usual dataset (bookmarks, contacts, etc).
3. The same song got copied back to the iPhone

Why the copy-back? Did the track change in some way? Was more info about it downloaded by iTunes after it was copied from the iPhone?

I can't say I care too much. The whole process was speedy, elegant, and enjoyable.