@vesuvius: looks very good. Unfortunately I also happened to notice a few things that constitute pet peeves of mine:
1) Shortcut on the desktop, without an installer option. Becomes a capital offence if deleting it requires admin powers (hello, Acrobat).
2) Notification area pollution. Yes, you may have a valid use case that I don't know of, but after years of abuse I adopt a "guilty until proven otherwise" approach on this.
3) Non sequitur notifications. If you disrupt my work (or my entertainment, for that matter) by popping a balloon in my face, it better be something that implies an action on my part (obligatory Raymond Chen link). "Backup started" doesn't qualify.
3.1) Also: I consider notifications are the last resort of communication. If the application is open (or, worse, currently active), that's where I expect to receive all the information I need. Having a balloon in response to a button click is as if you went to a restaurant and the waiter, while taking your order, texted you "I'll bring the drinks in a minute".
Yes, I know I am overreacting. It's just a lost battle I've been fighting for too long.