Simple, post a screenshot that shows off your favorite feature(s) of OSX.
Late 08' 2.4Ghz MBP, 2GB of RAM. Easily using and navigating through 35 Safari windows while browsing Digg and catching up on some news.
Almost couldn't figure out how to capture drag and drop. I love how I can just drag the picture from the internet into the artwork tab of iTunes and it applies it without any stupid extra steps.
I always did that in windows until I got my mbp.
I think drag and drop is vastly more intuitive in OS X than it is in windoze and this is only one example but I haven't installed the 7 RC yet so we'll find out.
There are a lot of features I really like in OS X but I would have to say the one I miss the most while using Windows is Exposé. The "Show Desktop" shortcut is quite primitive in comparison.