I had it on my nikon d40 and used it quite a bit. all I did was set a minimum shutter speed and max iso (usually 1/160 and 800) and i was set. it worked quite well really

my new d90 is even better with this

as to why canon dont have it... who knows. they just arent as good as nikon i guess

...this said i dont always have it on, in fact i only have it on when the situation dictates that i might need it, but its bloody great