I shoot d700 so file sizes are probably similar.
On my 2009 MBP: small delay while images load/render around 1 to 3 seconds. This 'annoys' me a bit but apart from that editing is very responsive. My 'dream machine' would solve these issues but nothing on the market in notebook form will do that.
On my rev b MBA: Files take even longer to render and then adjustments like levelling (tilting the image), cropping, adjusting the tone curve are slow and can result in beach balls.
Bottom line I can sort, process, adjust and tag images on my MBP in a swift and painless workflow. On my MBA it is 'picture by picture' editing and I have to be patient. Ok for fiddling with the occassional shot but if I have an entire batch from a large shoot I wait until I can get the files on my MBP.
Overall the MBA is great. The SSD makes it snappier than my MBP for boot/reboot and launching apps like firefox, safari, word etc. But for Aperture it let's me down and it also occasionally overheats and becomes stuttery when e.g. on a youtube marathon.
I am interested to see what they manage with rev d, but sometimes I think about getting a 13" MBP instead for a more portable photography tool. Saying that, the weight difference between the 15 and 13" MBP is marginal, whereas the MBA is awesome for business travel. Just a shame it doesn't deliver for RAW editing.
I am pretty much convinced that anyone telling you MBA is great for aperture is shooting jpeg from a compact camera...