Yes they are essentially the same monitor. As to how much it will affect you, that really depends on how picky you are. When I play the football game on the UT2K3 demo it's pretty bad. If you look at a part of the map with lots of glyphs on the wall with a black background the blur is very noticable. Black parts of the wall will bleed when you strafe. Some people aren't bothered too much by it because if you don't pay attention to it you might not notice it. On the other hand sometimes it gives me a headache because with high speed movement everything sort of blurs and I am used to the sharpness of a CRT monitor.
The thing that bugs me even more about the Dell monitor is actually web surfing. When I go to websites which utilize black alot like the Starcraft Ghost website you will notice the ghosting. I don't know why but the monitor seems to have a very hard time dealing with black, while even my older NEC LCD can perform better.
This subject is hotly debated because it all comes down to a matter of perspective. I purchased my Dell 1900FP less than 2 weeks ago and I am selling it now because it bugs me. Other people have said they liked it and you can even find reviews saying there is no ghosting at all. On the other hand you can find reviews like Anandtech's, my own perspective, and some other threads that complain. Look around I saw a few threads complaining about the Samsung 191T (one said Madden ghosting was so bad he couldn't see who had the ball).
Don't get me wrong, other than that (and a little color mismatch, the monitor is more red than my NEC LCD or Samsung 1000P 21 inch CRT even with the same color settings) it is a fine monitor. It has a very thin border, is very light and compact. The benefits over CRT are also good such as automatic geometric corrections etc. However as with all LCDs quality will suffer if you try to run it out of the native resolution. Even though you have a Radeon 9700 Pro the problem isn't running it at good FPS, it's finding games that support the resolution (weird ratio as compared to CRTs)