Agree. We have quite complicated rules as we have many different paths for alert escalations, different groups are responsible for different things on a host, some have out of hours, some don't, etc.
It's a pain having to open two tabs and flick back and forth when a clone function would save time and help reduce errors.
Personally I would be happy for the alert rules order in the UI to be the order in which they are actually processed and let the system manage the order. I'd like to be able to simply drag and re-order in the UI.
The ability to test a rule from within the rule definition would also be useful.