I recently bought an ASUS 1215n and it's pretty good for a 'netbook'. It's got the latest nvidia ion2 and intel atom d525. It's able to play most games at medium to low settings (as long as you keep expectations low), it can mulititask pretty well, can play hd videos fine (1080p in full screen on youtube still is slightly slower framerate than desired, though I assume this is a flash thing as the ion 2 is still new), it has up to 7 hours of battery life (5 with the wireless turned on and the wireless running and maybe some videos etc. ).
Some down sides: I'm experiencing some wireless connectivity stability issues, though not sure if this is my network or the computer. The keyboard is a little frustrating, the keys are smaller than I'd liked and there's a little flex on it - hence the typos in this post. And asus aren't great for customer services.
though i should say it's a 12.1 inch netbook, not 13 inch, but the screen is 1366x768 for HD optimization an it's large enough for me. and of course, it sure doesn't break the bank compared to say an imac/book.