I think my enlarger can do 11x14 and maybe 16x20 but I've never printed anything larger than 8x10 myself.
I'd guess that sizes of my prints are distributed roughly as follows:
60% - 4x5/4x6,
30% - 5x7
10% - 8x10.
I do look forward to printing 50x70-ish one day, I have a lot of the equipment but not the permanent space that would allow me to do it right. I can see doing 30x40 in the near future though...