Here's a comparison between the Roku and Apple TV2. It appear that if you are into Apple stuff then the TV2 is the way to go. However the Roku does more for the same price and you don't have to jailbreak it.
If all you want to do is watch Netflix then the cheapest Roku is the way to go IMO.
"It does not take a majority to prevail... but rather an irate, tireless minority, keen on setting brushfires of freedom in the minds of men. " -- Samuel Adams