graeme_p - 5:27 am on Feb 26, 2010 (gmt 0)
So there are a total of
6 that use Trident
3 That use Gecko
2 that use Webkit
1 (obviously) using Opera's rendering-engine-I-can-never-remember-the-name-of
Not counting extensions that allow you to switch rendering engine.
SO half the choices use MS's rendering engine.