Short(ish) story on wide gamut - when displaying standard content, primary colors look over saturated, almost neon. When working in Photoshop you can use color profiles to correct this, but everything else on your computer (OS, icons, web browsing) looks out of whack. Some people don't care, or think more colors = better. If you edit on wide gamut, and then put it on the web, everyone else is going to see your images as dull/undersaturated. As a graphic designer I assume colors are an issue for you - you could choose to embrace it (and the inevitable headaches) or, more likely, if you've been happy with your ACD - just avoid it.
Your computer by default assumes an sRGB color space, since that's what pretty much all content is designed for. OSX has historically ignored the existence of wide gamut (because Apple's displays don't use it.) For example your computer sends a signal to the monitor that says "display 100% red." When your wide gamut monitor receives the "100% red" signal, it displays what it thinks is 100% red. Which is some retina-burning version of red that was not part of the original image. Photoshop can correct for this and will instead send something like "display 78% red" for the same image and it will look "correct."
So basically you are paying a premium for wide gamut when you probably don't really want it. But then there aren't any 30" alternatives without it. I don't want to scare you off too much from the Dell, I haven't used the u3014 - the sRGB mode may well be improved over the u2711. Being LED instead of CCFL now, it is an entirely different technology. I would just purchase from somewhere with a decent return policy.
If you happen to live near a Microcenter - this
AURIA EQ278C for $500 is a really interesting option. It is an sRGB IPS that does 2880x1620 - so even more pixels than the 30." Looks like it is available elsewhere online (for more $) and there is a
30" version, also 2880x1620 - but that panel shows 1.07 billion colors in the specs - which would indicate wide gamut, but then the specs on these "cheaper" displays are so difficult to verify. Heck the 30" is $700 after rebate at
Tiger Direct... now -I- want one...
If you do shop the Aurias - note there are two 27" versions. The EQ276WN is a native 2560x1440 panel that does some goofy up-sampling to 2880x1620. (but looks fine at native 1440p) I think the details on the two 27"s on the B&H site specifically are reversed.
Well that got long, sorry if I've confused things...