1/8" is pretty popular, but I think that's because people overestimate themselves. Many pro trackies use 3/32" without any problems.
I run 1/8" but sort of wish I'd picked 3/32" these days. It tends to be quieter and more available if you're running road cranks. My track bike and road conversion both have 3/32" rings and 1/8" cogs. My mountain bike features 3/32" all around.