How are you using a full 8gig of ram?
Fired up Activity Monitor and launched....
Virtual machine for Win7 with 2G allocated (Word/Excel/HTML checker/IE/Outlook), virtual machine for Ubuntu with 2G allocated (FireFox/Chrome/Evolution/Music Player/Shotwell/OpenOffice Writer), Photoshop with 30 pictures, Illustrator with a heavy 4 page design, Dreamweaver, Excel with a decent sized spreadsheet, Google Earth, Word with a big 50 page image laden document, iPhtoto, Quicktime with a 9G movie, VLC with a 640M movie, iTunes, StarOffice with same big 50 page image laden document, Chrome, FireFox, Safari, and a bunch of other programs.
...watched Activity Monitor as memory filled up, started swapping, and now 1.26G of swap has been consumed.
I need to do a little reading on free vs. wired vs. active vs. inactive vs used, but I can feel the system slow down a tad once I started swapping. Probably need a more official way to test, but this is as "real world" as it gets.