Forms (show and process) on the same controller or on different ones?

Both the previous answers are contain good ideas IMHO.

I had been doing it all in one method, before the if/else fiasco finally wound me up enough that I thought it would just be easier to have two separate views and methods for update or create. (Although I would definitely keep it all in one controller). The additional repeated code is not too substantial. A pain though when the form keeps changing, having to update two views and two methods.

The back button on the browser causes lots of work/problems as well, still have not found a reliable and cross-browser way to prevent the 'do you want to resend form data' browser message etc.

Paul.