I currently game on a 19" 75hz LCD. I had a 60hz 23" Philips but gave it to my brother as 60hz drove me insane with how slow it felt.
I would be upgrading from 1440x900 to 1920x1080, I guess I may as well take a shot with the Samsung on sale at the moment for even if I don't notice much improvement over 75hz at least I will have a much bigger screen
23", you say? Did it happen to be 1920x1080, too?
1920x1080 gives 2073600 pixels
while
1440x900 gives 1296000 pixels
Meaning with your 19" you needed only 63% of the horsepower you needed for the 23", to get same framerates. Now, 40% difference is quite noticeable, so are you sure it wasn't the performance hit that made it feel slower? Or did you already account to this, and leveled down the eye candy when playing with the 23", to get approximately same framerates?
Btw, if you do end up getting 120Hz, it will most likely be 1920x1080, so the same performance hit is something you should anticipate for.
PS. I've been playing with 120Hz CRT @1024x768 with GTS250, and with slightly older games (like first F.E.A.R.) it's pure awesome. But with newer games the eye candy takes the performance hit (even with 1024x768), and the smoothness is gone. So make sure your gear is up for the task, if playing mostly newer games.
edit:
Actually, you should try playing with sufficiently older games, where you can be sure your gear can give full framerates on both resolutions.