Emacs is slow to open, and there is a lag when moving the cursor position, opening files, and searching within frames when emacs is in maximized/full screen mode -- it's ok when it's only taking up part of the screen.
gedit appears to be ok, and running emacs in no window mode (emacs -nw) and No-X mode (emacs-nox) works great - things are snappy.
This system is an Intel quad-core box with 8gb memory. It has two nvidia cards, and three monitors.
Dual-head card: EVGA GeForce GT 520 Graphics Card Video Card 01G-P3-1526-KR
Single-head card: ZOTAC GeForce GT218 (ION) 512MB DDR3 DVI/HDMI PCI Express 1 Graphics Card, ION-GPU-A-E
I had been running both cards with three screens on Fedora 14 64bit, and everything worked fine. But when I upgraded to Fedora 16, the kernel and nvidia drivers upgraded, and things started running slow.
For example, in emacs, adding new lines to a file while it's fully maximized caused a lag while the screen redrew/repatined, as the lines slowly moved into position. If you hold down the backspace key and release it, it will take a few seconds for the cursor to stop and complete. It's like a buffer or repaint/redraw issue.
Things improve somewhat when I disable the GeForce GT218 card and only run two screens, both on the GT520, but there is still a lag in emacs when you backspace over a series of characters.
This happens in both Gnome and XFCE so it's not specific to Gnome. Gnome 3 is running in fallback mode, and I switched to XFCE thinking Gnome 3 was the culprit, but the lag remains.
Fedora 14 was fine, and all the hardware is the same.
$ uname -a Linux love 3.1.2-1.fc16.x86_64 #1 SMP Tue Nov 22 09:00:57 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux
nvidia bug report attached here... http://www.nvnews.net/vbulletin/showthread.php?t=169199