Can I let a few blooms open just for the sheer joy of pretending it is spring? or do I need to be merciless and snip them off?

Do some of both. :) It does slow vegetative growth but some are going to bloom no matter what you do. As long as you remove the majority of the blooms before you transplant them to their final growing place they will kick back into v. mode.

Dave

Thanks Dave - thats just what I wanted to hear. I have been cutting back the runners that the petunias shoot out so they will branch close to the base of the plant, but there is a bloom forming in the center that I just couldnt make myself snip off.

I usually top the Dahlias after the 3rd or 4th set of leaves, but these are shooting out laterals so well that it seemed unnecessary, and now there are a few buds, which seems really early, but makes me happy!