Thanks guys for all the replies, and for the video link, very helpful. I am considering the 1d mark 3 more at the moment, as I do love the speed and I do shoot sports from time to time, I rarely print large, and I have got used to the 1.3 crop so this isn't an issue, I have a few wedding coming up starting at the end of june so I have couple of months to decide.

thanks again

TIm

Personally I'd just keep using the work camera as it's unlikely anyone is going to check ;)

Otherwise, if you are going to be shooting sports then I'd think that a 1D series would be a good choice. My feeling is that almost any camera would be absolutely fine for use in a studio, for portraits, weddings, press, products, wildlife, landscapes - nearly anything. Sports photography, however, does put extra demands on the camera. A fast frame rate helps as does the speed and accuracy of focusing, and these are the areas where the 1D series is supposed to be better.

I've been shooting sports events with my 40D nearly every weekend for the last few months. It works fine and I'm mostly really pleased with its performance. Have to say I'd still like a 1D series camera at some stage as I think it would offer advantages. For example, jpeg files straight out of the camera are supposed to look a lot better and need less in the way of tweaks.

A lot of the sports leagues etc are coming to an end around now however so maybe I'll just hold off for a while yet.

For anything other than sports, a 5D might offer the best performance (not to mention bang for buck).