I just got it and initial impressions of build quality are excellent. It's mostly plastic, but it's the hard as wood type of plastic and feels very sturdy and solid, with no 'creaking' sounds you normally get when handling cheaper monitors. The stand is very well built and very intuitive to use, and provides pretty much all the adjustments I need (height, tilt and rotation). The screen surface has a smooth matte texture and gives off no reflections or glare. Also the styling is spot on, very professional, sleek and clean looking.
As for the screen itself, as soon as I turned it on (without any calibration), I instantly noticed a big difference coming from my 22" TN panel (3 yrs old). The blacks look very black, almost like ink and whites look more white. Colours look impressively vibrant and deep, but more importantly, everything looks much more consistent across the whole screen. In comparision my old TN looks dull and washed out, with blacks looking a complete mess. Plus the slightly tighter pixel pitch makes everything look a bit mroe crisp.
Movies look jaw dropping, literally. Just watched a good 30mins of Avatar (1080p), even though I just put it on for a quick test, it looks that good. As SushiCat said, everything that is colourful, looks beautiful and really catches your eye.
Response times seem more or less the same as my TN panel (2ms), though there does seems to be slightly more blurring when dragging windows across the screen; nothing major though. Using a HD5870 I haven't really noticed any stuttering at all in movies, appart from the usual juddering you get when watching 24fps movies on a 60hz screen. Haven't tried any games yet, but I expect a similiar story.
Thankfully, viewing angles are superior to my previous monitor and while there is a reduction in contrast when viewing from an angle, it's nowhere near as bad as I thought it would be and the main thing for me is that there's no noticeable colour shift. From extreme angles I did notice a slight purple tint in the corner, but it's not huge and from a such a stupid angle, it's irrelevant to me. This is all in dull daylight conditions (not very bright).
Unfortunately I recently moved into a converted loft and haven't had the time to install curtains, so I can't really tell how the panel will perform under dark conditions, but so far I'm very impressed.