Purchased MBA last week and upgraded to 10.7.2 and latest EFI.
U2711 stays blank when I connect via mini-DP-to-DP cable (from DeLOCK), no freeze though. U2711 wakes up briefly when I click "discover monitors", but goes back to stand-by immediately. Lower resolutions work, though. The Dell's DP is working connected to PC.
I know people have posted about this before, but there doesn't seem to be a clear answer. I phoned Apple Care and Dell but they could not offer a solution.
I don't want to use the Apple mini-DP-to-Dual-Link-DVI cable as it is bulky and needs a precious USB port to function, not mentioning it costs 99 Euro. This should work with DP as advertised.
MacBook Air, Mac OS X (10.7.2), latest EFI (as of Dec 1st 2001)