Well, last time I checked there were very few (if any) monitors that had a matrix other than TN that could do below 8 ms or that wouldn't use dithering, as they were 6-bit panels (they display less colours and try to fool human eyes), and the differences aren't really that apparent in most cases as far as 'ghosting' (afterglow) is concerned.
What you're more likely to notice with panels with a fast response (below 8 ms, either gray to gray or black to black) is that there's often banding in gradients they display when there should be none.
As have mentioned, they also tend to be able to display less colours, trying to save that with high values of static and dynamic contrast, which often pronounces the defects of the technology, especially with TN matrices.
That doesn't mean they're bad office monitors, they just suck for photos and artistic stuff a lot.
Also, pixel pitch is somewhat important. You're likely to notice that 20" have a pixel pitch of 0.255, which is the least of LCD monitors of sensible prices these days as far as I know. It results in the image looking smoother, which is particularly apparent when you view lines.
Last but not least, the price difference between a 17" and a 19" LCD monitor isn't really big now. I've had decent experience with Philips 190S7, which some of my friends have and while it's not very good for photos, it makes for a very good office monitor. The new 190S8 shouldn't be worse, but try to google some reviews if you don't find the 190S7 in stock anywhere. The 190B7 and 190P7 should have class I panels, meaning there shouldn't be any bad pixels in their matrices.
One warning: try to avoid widescreen LCDs, especially the cheap ones. They tend to have poor backlighting, with edges being of different brightness that the centre, their panels aren't usually that great either and I could see that last time I had the opportunity to look at one. It was either an Acer, a ViewSonic or a Philips, I can't remember now.
It gets better with bigger ones, e.g. a 24" HP monitor I saw was pretty good, but I could still see the imperfections.
Then again, I've been spoilt by Eizo
Here's a brief user report on the Philips 190S8:
http://www.xbitlabs.com/forum/viewtopic.php?t=13813 (use ctrl+f to find it).
Philips 200P7ES is well rated, for photo work too, but it's a bit expensive. P is the 'professional' line of Philips' monitor line. S stands for Soho (small office, home office) and is the cheapest line (still better than most low end - middle ranking LCDs of other brands in my experience, though), B stands for Business, they come with zero dead pixel warranty like the P line-up (the 19" ones, that is).
Also, have a look at the list near the end of this page:
http://www.xbitlabs.com/articles/other/display/lcd-guide-f2007_4.html#sect0
This article might be worth skim-reading:
http://www.xbitlabs.com/articles/other/display/lcd-guide-f2007.html