I just set up my first dark room, and I was pondering the same question about 35mm printing as that's my format. My conclusion was to buy an enlarger that could handle MF, just in case I was dissatisfied with the results from 35mm. But everything else (trays, easel, chem storage) was purchased with the plan of 8X10 max size. So far I'm really happy with the 8X10 size, especially with a slower film like PlusX for sharpness, or something speedy like Tri-X @1600 to show off the grain.

I am planning a MF purchase, but I'm not sure if I'll be going higher than 8X10 with it, at least in the short term. I only have so many walls, and the open spots are better filled with smallish prints.

The Ken Rockwell thing - any press is good press, I guess.