I currently have a 2011 11" MBA with 1.6 i5/ 4gb memory/ 128gb. Would the 2012 air be a noticeable difference or should I consider the rmbp? Size is an issue since I travel all the time. Use it mainly for email, spreadsheets, and basic Internet.
I purchased the 13" 2012 MacBook Air when it came out in June primarily for university. Although I liked the size of the 11" I wanted/needed the most battery life I could get and hence I had to go with the 13".
I put my MacBook Air on Ebay last week and purchased the 13" rMBP on Saturday. Although it is 500 more here is why I think it is the best way to go (for me):
it is only slighlty heavier
apart from the wedge it is actually physically smaller
the screen IS amazing --> color accuracy, viewing angle and high DPI count makes it very easy on the eye for reading all of my medical ebooks
it runs quieter then the Air --> tested with several games in Windows
Although the price is very steep (especially if you go with the bigger version which brings you close to the 15" price range which would be the better value proposition then), I wouldn't want to go back. Clearly it was made with Haswell in mind and I'm sure it will rock completely next refresh. But right now for everybody who needs to read a lot on a computer screen this is a no brainer!
Either computer would fit your needs, it's really up to how much you want to spend and what you want. The 13" Air is a little more portable than the 13" retina, although probably not enough for it to be a deciding factor. I expect the MBA to run a little faster than what you currently have, but probably not noticeably unless you're doing anything graphically intensive. I'd say go to an Apple store and have a look and see what you like best.