I use them for 2D gaming only and I will attempt to take the LG to my grave. The Acer is just sort of meh. The lack of input lag and low response time make the LG a true replacement of a CRT. I couldn't be more in love with a piece of hardware and I consider it the best hardware upgrade I've made since ~1998.
(I can't recommend every aspect of the LG, the stand, bezel, OSD, buttons, lights are all really really bad)
I don't know about 3D, but I really hope more hardware reviewers tout the awesomeness of a 120hz LCD in 2D. If they have a hard time doing that based on experiences with monitors like the one in this article, go get that LG to compare.
/signed, passionate FPS gamer