I can play two comfortably but usually just play one, and devote some attention to other matters on the side. I think more than two is too many for me. Full ring I can do three or four.

I agree with the opinion that 6max is too fast and too dependent on reads for heavy multi-tabling to be a good strategy. I win a lot of hands a day that I wouldn't if I didn't have such a good read on my opponent.