Their thunderbolt ethernet adapter is $30: http://store.apple.com/us/product/MD463ZM/A
Even when setting up hotdesks for guests, it's unclear if you could put just a TB display in them -- enough people will have non-TB macs, or non-macs, to require something else. Maybe you could have some percentage TB display, but a good third-party dock + a display which can take multiple inputs (DVI, HDMI, MDP via adapter, TB to adapter to monitor) seems like a better choice. Uglier, yes.
For personal/home use in a dark room with only 2011+ macs, and if you have a spare 15" for other temporary use, then sure, it's a good option.
Keys/wallet/etc. remain in pockets when not in use, though -- so they're a LOT less likely to be abandoned than something which is small, connected to another long cable, etc.
Kind of silly given that the new Macbook Pro Air HD Super 15 has a better display than anything else I own, so I'm not going to necessarily want to put a 1920x1200 24" or even 2560x1600 30" in the center of my desk with it -- I'd treat the laptop display as primary, on a stand, with a keyboard. But Apple doesn't make a docking solution, and the Belkin/Matrox docks have been vaporware for over a year.