I say yes.
I was using Playback to stream to the 360. The ATV2 interface alone is far superior, which should come as no surprise.
How?
1. Easier to find movies songs, photos. I'm watching the movie on the ATV2 before I can even get to the movies folder on the xbox.
2. Updates to itunes (new movie, coverart, etc) don't always show up on xbox without a cache reset. (instant update on ATV2)
3. The big one: The xbox won't accept the higher bitrate/framerate settings on Handbrake of either the ATV2 or High profile preset. Works fine with the ATV1 preset. What this meant for me was unacceptable picture quality for the xbox. (choppy motion on slow pans, fuzzy detail) On a 50" plasma, i have to run the Handbrake RF to 17 to get acceptable detail, even though most people say you can't see the difference below 18 (I can, and I have 40 year old eyes).
4. ATV2 you can turn subtitles on and off for your rips, no on xbox.
5. I can stream my local radio stations via itunes, on ATV2. xbox/playback won't accept streams thru itunes.
Are there things I wish the ATV2 could do that it can't or won't? Yes, and I haven't bothered to JB.
The ATV2 youtube interface sucks. It seems to want to cache the entire stream before allowing it to play. Frankly I find it unusable.
The bottom line is this: I wanted the xbox to do it for me, I really did. But in actual use, it was too clunky for me. The ATV2 gets used all the time.