Purchased the 1D MK IV after waiting patiently for Canon to upgrade the MK III and putting up with the sluggishness of the 5D. Mine has gone back to CPS 2x, and now a third time due to inconsistent focusing issues with Single Shot mode. They've acknowledged the camera needed adjustments each time, but I'm perplexed why they can't seem to nail this completely. My 5D is beginning to look better and better, though it's slowness and crappy LCD pains me.