For jobs with complex sets of parameters, it would be really useful to have a 're-run' button on the build page, that would open the 'Build Now' page for that job, with all parameters initialised to the values they had for the selected build. That would allow the user to modify one or more of the values before running the job again.

I would find this great for the situation where I made a mistake in the set of parameters and had to run again, or wanted to release the same build with the same comment to several different environments.