I bought the Roku 3 because it has more content. YouTube is easily side loaded; I did it in less than 5 minutes on the day my Roku arrived and I'd never sideloaded anything in my life before. And there's Twonky for 'airplay'. And, of course, Plex. And 1,000 other channels and counting everyday including Fandor. And a microSD slot and USB connectivity for a hard drive. And you can plug your headphones into the remote which seemed kind of silly to me until I used it and was able to conveniently block out a month of sewer pipeline drilling next door by putting in earplugs under my Beyerdynamics plugged into that remote. It cost $99 compared to the $75 the Apple refurb store asks for the current but now last gen tech aTV.
Assuming Mavericks really does allow the TV an aTV is hooked up to to be turned into an additional monitor and they get a freaking app store for the thing, I'll definitely consider getting one.
I think it's a bad idea, however, to make the device any more reliant upon the user having an iOS device. My 70+ year old mother and stepfather have started streaming Netflix this year and they'll never buy or want iPhones or iPads but an easy to use streaming box with a remote would be a lot more enjoyable for them than using an HDMI cable and adapter and audio cord hooked up to the tv and having to keep getting up to go back to the desk to choose the next episode or a different show, etc. They don't even know how to use the DVR they get with their cable and have never used it and refuse to learn. And it took my mother nearly a full year to remember how to change the input from the cable box to her MacBook and back. So, for likely future users like them, a really simple remote with like 3 buttons and no need for any other 'confusing' devices is really best.