I love proofing my negs at 11x14 inches. That way I can really see what's going on with the grain / separation / etc.. From there, it's all rolls! I guess it comes from the days when I was doing paintings where I just started to see and work big. I can't count how many times I wanted to embark on a project that involved small intimate prints only to fail miserably!
In the end, I LOVE 30 x 40 inches! It sounds crazy, but for me it's large and imposing, but still really easily managed in the darkroom.
... now if they can just keep some large rolls in production I will be a happy printer!