Well I upgraded from a thinkpad to a mbp13. And I was looking for an UPGRADE when I did that!
But in terms of display and weight it was a downgrade. And it terms of performance the SSD and i5 isn't that much better than what I had before. I always have my computer in sleep mode anyway and probably the heaviest apps that I use are chrome and itunes. So it doesnt feel like it would blow the thinkpad out of the water regardless what the specs on paper say. I also wanted to do some mild gaming which I couldn't do before on my old laptop but yeah I gave up because I am just not into hardcore gaming.
The mbp15 would be an upgrade and a downgrade at the same time. Upgrade because of hi-res glossy screen. Downgrade because of size, weight and money. I am not sure about the mba13. It seems like it would just be a lighter version of the mbp13. So I was really hoping new macbooks would come out buy the end of the year. I don't know how long I can stand using this laptop.