I've been using the TD for a year with a 13" MacBook Air. While watching the keynote at WWDC I decided to gently and lovingly kick the Air to the curb and upgrade to the rMBP. I use the TD as a dock, connecting all manner of Firewire drives, USB drives and a CD drive through the TD. For the most part it has worked great. The only issue I have had is in the Mail app.
When "hot" docking the rMBP (i.e. with it powered up), Mail appears to be fine. However scrolling either the 2nd (message) or 3rd (preview) columns causes display issues. Scrolling slowly causes the text to go out of focus. Scrolling fast causes it to smear. This happens ONLY in Mail. All other apps are perfect. It does not happen if the rMBP is powered up after connecting to the TD, only if it is connected while powered.
Using Code Krieger's gfxStatus app (
http://codykrieger.com/gfxCardStatus) I have discovered that the TD requires the nVidia graphics chip to be used. His app allows you to force the graphics mode. If I force it to integrated, the display goes off, and on one occasion caused a kernel panic crash. After rebooting from the crash the display was perfect, even in Mail. Once Mail works correctly, it stays that way all day. Undocking with power on also works fine, using the rMBP screen as the display.
While this could be some kind of weird chip problem, I'm not going to address it with Apple until I install Mountain Lion to see if that works differently. In all other respects, the docked rMBP is a dream to use. It's scary fast, cool running, and in all respects the best computer I've ever owned. The combination of it and the TD gives me a fabulous desktop that I can take with me.