- Rate items - In terms of interacting with your iTunes library and being an extension of it, the Apple TV is more of a 'dumping grounds' than a try syncing device. Outside of removing media files when you uncheck them in iTunes, the Apple TV is more or less incapable of truly *syncing* with your library like an iPod does. Case in point: rating items. There's no way to add 5 stars to that rockin' song or video from the Apple TV. However, to be fair, you can't rate videos on an iPod either.
- On-The-Go Playlists - This one is a particular bummer for me, as I use On-The-Go Playlists on my iPod quite a bit.
- Sync from more than one computer - Apple has been pretty up-front about how syncing works vs. streaming (you can stream from up to 5 sources), but I figured it was still worth a mention in case anyone is still curious about how and from where the Apple TV can actually snag its media.
- Enable shuffling - the iPod has a master preference (under its Settings menu) to turn on the shuffle feature across the entire iPod - why not the Apple TV? Each list of media (all songs from an artist, an entire playlist, etc.) has a Shuffle option at the very top, but this means I need to begin with using that shuffle feature - I can't enter a list of items, pick one that I'd like to start out with and let the shuffle kick in afterwards.
- Interrupt a shuffle - Speaking of shuffling - a feature Apple made quite a big deal over back in the day and even named an entire product after - it's beginning to feel like the company took a step backwards when designing the Apple TV's experience. If I begin a list of items with that aforementioned shuffle option and later select a specific song I'm jonesing for, the shuffle is broken; the Apple TV begins playing the rest of the media items in order.
- Display a video timeline - when watching any kind of video, the Apple TV cannot display a timeline without me having to either pause, rewind or fast-forward said video. This is a particularly jarring UI quirk, as I was watching that Camino tech talk on my Apple TV and I had to interrupt the experience just to find out how much time was left.
Ultimately, the Apple TV is still a 1.0 product though, and Apple will surely tweak aspects of the experience with software updates as users begin sounding off on what's missing. Besides the obvious gripes that have already been mentioned to death - no 1080p output, small hard drive, etc. - who else has gripes with the Apple TV experience?