Well count me among those waiting for 4GB. I'd buy one now if available, though would also like to see a 256GB SSD option as well.
My 3+ year old MBP has 2GB of RAM and I've found by carefully watching the system monitor - in particular the Swap use - that it really does slow me down given my usage.
Interestingly (to me at least) is that my usage feels pretty basic on the whole, i.e. something for which I'd think 2GB ram would generally suffice. I usually have mail, ical, contacts, safari (4-5 tabs) open all the time, and weatherdock as well. Add an office app or two from time to time (sometime MS, sometimes openoffice) and I get lots of spinning beach balls and increased Swaps. FWIW I'm pretty good about managing free space on my HDD.
But my usage really seems to want 4GB ram...