I also just installed and have 3 things to report.\
1. All DiskStation apps now correctly support quick connect which is quite helpful. You can use the quickconnect id to connect outside fo the network like normal and seems to work flawlessly with no bugs.
2. AirPlay works through the Video Station package and app for iOS. IT IS NOT HOMESHARING. It works by opening Video Station (Or Video DS for iOS), selecting your movie, pressing play, then pressing the AirPlay button in the bottom right corner. It works exactly the same way as iTunes.
It's like a broken iTunes as far as dishing it out. Media that was formatted by Handbrake and works in iTunes gives a "An error occurred loading this content." on the ATV3.
I also got this error the first time. I fixed it by either A) allowing the video to play for a couple seconds before AirPlaying or B) After you get the error, press the Play button on your computer/phone again. Both of these will solve the problem. It also seems to be random which ones of my files will produce the error. Some will, some wont.
3. Transfer speeds from my Mac have increased DRAMATICALLY. I was getting constant transfer rates of between 30-40 MB/s, I am now getting closer to 70 MB/s on a constant basis and have spiked to 90MB/s on more than one occasion. The speed increase is immense and really helps with network transferring!
This is on a gigabit wired LAN system through a Netgear 5-port switch and a 1 year old Airport Extreme.