Well, I've made my decision. I've been able to actually get a quick use of a 1080p 27" monitor with a TN panel and that resolution at a 27" screen size would simply be unacceptable to me. I had a long think about it and came to the conclusion that downgrading panel type (S-PVA to TN) and resolution (1200p to 1080p) while at the same time increasing panel size would be madness.
The TN panel also made the colours look a bit bland compared to my 2407WFP not to mention the crappy viewing angles. The 2407WFP also has a much crisper image, and I suspect it will be even nicer on the 1440p 27".
Input lag has concerned me slightly, though I suspect I just worry too much, I don't even notice the 20ms lag on this, so I doubt an extra 10 will make the slightest difference to me personally.
I was also put off because the U2711 was not LED. I had erroneously thought that they were somehow higher quality. Now I realise that they just allow for thinner panels, and lower power consumption.
So I'm gonna pull the trigger on the U2711 on friday hopefully (pay day) and it's gonna be paired up with a 7970, should have plenty of grunt at that resolution yes?