I’ve been very impressed with the 27″ IPS-ZERO-G Slim Monitor WQHD 2560×1440 – Dual Link DVI, VGA from Monoprice. At just under $400, this was an excellent purchase for the money.
It is disappointing that it uses a DVI connection rather than HDMI but with my Mini DisplayPort to DVI Adapter, also from Monoprice, hooking up my MacBook to the computer has worked great. I have not compared this side by side with an Apple Thunderbolt 27″ Display because ignorance is bliss. At more than twice the cost, I can’t imagine the Apple Thunderbolt being that much better that I could justify that cost.