I have a 13" 1.3 Ghz i5 Macbook Air. I regularly get 11-12 hours of battery life. The new MBP advertises 10 hours of battery life. If it really does get 10 hours, that's probably enough for me in most cases, but if it's more like 9 hours I'd be inclined to keep my Macbook Air. How accurate has Apple been in battery life estimates for its most recent MBPs?