I use a few. Mystic View is reasonably fast and does the job. More recenlty I've been playing around with LoView, which has got a nice interface but is not that fast. Infact none of the viewers I've used are fast showing very hi-res pictures (A4000D as per signature) so I always re-size images from my DSLR to 640x480 using jpgtn (find it on aminet).
Weed
