Before anyone goes jumping on the "best ones" from Dell, take a read through this 35 page support discussion about their UP2414Q:
http://en.community.dell.com/support-forums/peripherals/f/35...
Anecdotal, but a friend and I both have problems with ours, and he got lucky with the 1.1 firmware revision (Dell won't let you upgrade it, you have to go through support for a replacement, and they'll send you a refurb that might have the newer firmware because they decided it would cost too much to update their existing inventory). And even then it might not work. He's waiting on Dell Support for his 3rd unit.
Do yourself a favor and wait until DisplayPort 1.3 is widespread and can drive a 4k screen without using Multi-stream Transport. It's not worth the headache.
Right now my computer is convinced that the left and right halves of my screen are separate displays and nothing will convince it otherwise. Other times MST will fail to connect and it only picks up 1/2 the resolution in the middle, with 1/4 width black bars on the left and right. From what I remember reading, Dell botched the DisplayPort handshake, and the workarounds that AMD/Nvidia have put into their drivers to try and fix it aren't 100%.
I need to return mine for backlight flicker too. But I'll write that off an an excusable manufacturing flaw that's going to pop up occasionally on some number of any model.
EDIT: Just for perspective, this is a screen with an MSRP around $1100, though we both bought ours on sale. The amount of shit we're dealing with for a screen that expensive is not reasonable.