This is a totally trivial nitpick, but when I see 500MB at the $9 level I start to do multiplication in my head and kind of get distracted. If it wouldn't cost you too much more, I would suggest considering 1GB for that level. The little story told by the levels just seems simpler that way to me. Like I said, totally minor point, and perhaps it's just me so take with a lot of salt.

Congratulations getting to this stage! The price levels seem reasonable to me. I personally wouldn't have a problem paying for it.

Is there integration with Basecamp or similar? That would be nice.