Well, I've had a few days now to play with my new ATV and compare it to my old ATV and I'll post up what I've found so far:
When I used to rent a movie on the old ATV it would buffer to the hard drive and was usually finished downloading before the movie was finished. EVERYTHING streams now on the ATV2 so if you start a movie and tell it you want to watch it later it simply stops streaming and picks up later. I'm worried this will be an issue if you have a flaky internet connection and I'm missing the "safety" of the hard drive in this case. Time will tell and our movie played perfectly last night.
Everything is shared currently/only via Home Sharing with ATV2 and full AirPlay functionality for IOS isn't here until November. Airplay will really make this thing shine I believe. I had to turn Home Sharing on with my iMac and you MUST have the new iTunes 10.0.1. Reboot your PC or Mac after turning on Home Sharing. Mine didn't work until I did that and then it was fine. Please note the new ATV2 will not show up in your iTunes like the old ATV as nothing is sync'd between the devices.
Video quality seems to be very good on an iTunes movie we rented last night and Dolby Digital worked just fine. There are NO video adjustments however on the ATV2. It's HDMI only and will output auto-detected 720P or 480P, that's it. 720P looks just fine so far though.
Screen saver has a lot more options now and can even stream pics from a Flickr account. This is pretty cool.
NO TV shows at this time in Canada. Looks like you'll have to deal with that on your Mac or PC and then stream them to the ATV2.
My existing ATV commands in my Harmony One are working flawlessly with the new ATV2 so no reprogramming required.
ATV2 has a new sleep mode that is programmable. The power draw on this thing though is very small and it seems to run pretty cool regardless especially compared to the toaster that was called the ATV.
There is a way to save favourites in the Internet radio same as the old ATV. Simply highlight the station you want and hold down the enter button on the remote and a menu pops up asking you if you want to save it. Works the same in reverse in the favourites menu to remove saved items.
I've seen a lot of complaints on the internet about wireless speed and stuttering with content streamed from your PC or Mac. I haven't seen any of that. It does seem to stream "differently" than the ATV but no problems for me so far. I'm using a new Airport Extreme and the ATV2 is locked on the 5ghz radio using "N" so no slowdowns. All my "G" traffic goes to the 2.4ghz radio. (on a side note: the Airport Extreme has seriously surprised me and has solved all my router complaints. Devices now stay attached and it even wakes up my wireless printer from sleep mode when I print. Love it! Anyone want to buy a slightly used Netgear WNDR3700 dual radio router?)
Now the big one....... NETFLIX! This is a really mixed bag so far on the ATV2. I have this on my PS/3 and it works perfectly so far on the PS/3 even over wireless "G". Movie information on the PS/3 clearly identifies if the movie is available in HD and some movies also show a 5.1 logo as well. The Scorpion King is an example with both and my receiver goes to DD5.1 from my PS/3 and the movie plays perfectly, other than a weird aspect ration problem with this particular movie but that seems to be a Netflix bug as the ATV2 stretched the movie as well.
I'm really liking the ATV2 Netflix interface, very Apple-like but it has some problems. First off it doesn't identify in the movie info if the movie is HD or 5.1. Second is video quality. It's very good and if you didn't have anything to compare it to you'd be fine but I honestly think the PS/3 looks slightly better with Netflix with colours being a little more saturated. Again, the ATV2 is fine and very sharp but it needs some firmware tweaking compared to the PS/3. Just a personal opinion though.
Biggest issue so far though with Netflix is NO DD5.1 support. I played The Scorpion King on the ATV2 and yup, Stereo only. I've tried every setting I could on the ATV2 for audio and no DD5.1 with Netflix. I've already called Apple and they're having a higher level Engineer check this out.
I may be wrong on this but I believe Netflix in the U.S. maybe doesn't offer 5.1 with their online offerings currently and may be doing an experimental rollout in Canada to test it. Maybe the Apple Netflix app is a U.S. version and isn't looking for 5.1 audio. Not sure on this one but I'm assuming it can be easily fixed with a firmware upgrade. Again, 5.1 on Netflix movies that offer it works perfectly on the Playstation.
That's it off the top of my head and apologies for the long post but hopefully this info is useful to some. Currently I have very mixed feelings comparing the old to the new one but I'm thinking I'll keep it for now and hope that it improves with firmware tweaks. The hardware is very powerful so I expect we'll see some serious improvements down the road. And heck, I've wasted a $119 bucks a lot worse than this before!