Did you ever try 20D/30D before? :dunno: There is a difference in AF speed. 20D/30D is at least 30% faster. The central sensor of 20D/30D becomes a sensitive cross sensor type similar to those found in 1 series when lens of apertures f2.8 or faster is used. Locks on faster in low light than 10D too.Wildlife is still ok. For sports or fast-action, might as well get 1D Mk IIn. Start up time is no big deal to me and AF speed is similar to both 20D and 30D IMO.