Good question. They are conspicuous in their absence. It will be interesting to see real world opinions of them in use.
I was interested in getting 27" IPS panel and wanted a thunderbolt dock. When I did the math, adding a $399 dock to an $800 IPS panel like Dell U2711 would put the total cost in the $1200 range. And that combo will not recharge a MBP/MBA.
So I am waiting for a Thunderbolt Display reforest to change USB 2 ports to USB 3. If that happens by end of October, I will be doing Thunderbolt Display.