I just picked up a Dell u3011 and I really can't say I notice the input lag. It's not enough to actually affect anything unless you stare at it right next to a faster display.
It's on sale right now too (until the 9th) for $1,150 which is 25% off. That's pretty much the whole reason I picked it up when I did.
Honestly I don't notice the input lag but I can't say I really have an eye for it. I like the choices with the input options and definitely think at $1,150 it's one of the better buys for a 30" that you can find with these features.
I do have to say though, with a single GTX 470 I'm really pushing the limits of this card. I just fired up Crysis and Metro 2033 and I had to scale back the settings to play at this resolution. So as always with a larger monitor, keep the performance in mind. I'm planning on doing a full rebuild when Oak Trail comes out though so I'm going to live with it for half a year or so