That's funny, a friend of mine just made the same decision last night: she ended up getting the MBP while the in-machine burner is still available. The next MBP design is alleged to have that eliminated.

I have a 2009 MBP (17", personal) and a 2011 Air (13", from work). I like the larger screen and better graphics card (relative to release date) on my machine, but the Air is super light and nice to lug around. However, the Air tends to stay attached to a 27" Apple display (also from work), so the display issue isn't really a big one (Terminal on small screen, everything else on big screen).

The Air performs like a champ but seems to have its fans ramped up often, even when running iTunes or a YT video.