When I get one of my Zeiss lenses working on my 10D, the results are very good, but as others' experience here also shows, it is a bit hit-and-miss, and on the 10D at least, down to focussing difficulties in some subject types. Forget sports or rapidly moving children (are there any other kind?), especially with longer focal lengths. I have tried ice hockey, and fencing, and even using a decent monopod, could not get consistently sharp focus. I suppose, really, it should be self-evident that I was using the wrong setup for such subjects. On static subject, however, it's a different story. When you have come from viewfinders like the RX/RTS, the 10D is disconcertingly awkward and tunnel-like, though I suppose too that I'm asking it to do a focussing task it wasn't designed for. As long as you know the logistical limitations, and match the kit to the subject, manual lens adapters are useful bits to have in the bag. But I tend to use mine now for 'special occasion' situations rather than being able to stick a Planar on every day.