I've been using ADW EX with a really nice ICS theme overlaid on it. Performance has been pretty solid on it. I'll give Samsung some credit though, they did a really good job of making TouchWiz 4 not a laggy experience. I work at an AT&T store and it's been the only stock launcher that has had really really good performance, but that's not what this is about, is it?
Here is a screenshot of my phone with ADW EX, with said theme, and a really gorgeous ICS Live Wallpaper
Click to view quoted image
GoLauncher EX is my launcher of choice. It is free and has a ton of free add-ons, and they update it frequently.