Mine arrived today. Setup was a breeze, although it didn't seem to work from my desktop (wired), and I had to set it up from my phone. It looks like it forces a peer-to-peer type of thing (phone - chromecast) where I access the ChromeCast remotely from the phone to enter the password of my WiFi router so I can connect.
Netflix and Youtube plays incredibly smooth, from phone, desktop, and tablet (HP Touchpad with CM 9). Buffering in the beginning seems to be ~10 seconds longer than usual, but after that everything plays smoothly throughout without any stutters. This was with my old trusty WRT54G too, although it's sitting there not 10 feet away.
The sweet surprise for me is that Plex actually works really well by playing it on the browser, cast the tab to ChromeCast, and hit full screen. I have an established Plex library already so playing local content that everyone was talking about is already not a problem for me.
Good stuff! :thumbsup: