Another PF790 vote here...just got mine as part of an awesome Amazon deal (+ a $50 rebate). It's geometry is every bit as good as my G400 Sony at work.
We have non-flat screen Samsungs in the lab and they have been OK.
I haven't seen the 900NF.
3 points for the original poster:
1. Your video card will be important as well.
2. Be sure to get to a store and take a good look at an AG screen. The thin horizontal lines don't bother me at all, but they drive some people *crazy*.
3. With regards to specs, try to get the opportunity to fiddle with someone else's 19 inch monitor. I run all of the 19-inchers at 1280 x 1024 (at 90Hz on the PF790). Depending on your eyes you may not be comfortable at 1600 x 1200, which makes some of those higher end specs moot. I actually found the higher refresh rates on my work Sony to be annoying and currently run it at 85 Hz.
As I'm sure you've noticed, picking a monitor is far from objective and picking one that you can't tweak to your satisfaction is painful in more ways than one!
Enjoy! I just got my new PF790 last week and it's really like having a new computer. Alright, so I also swapped in a MSI Pro 2A + 1 Ghz Tbird...wheeeee.
Happy New Year,
Fraz