We did a trip out of Crabtree the 3rd week of August last year and had no bug issues. We had been warned that it could be bad so we came prepared with deet and headnets...maybe we just got lucky? I slept in a shelter with no netting and didn't have any bites.
As far as crowds, that wasn't bad either. We ran into some horse packers, CCC workers, and backpacks, but no large, rowdy groups.
The hike up from Crabtree to Gem Lake is very nice. We went in further to Buck Lake and spent a few days fishing and doing some off-trail hiking. We made it a loop by heading out past Wood Lakes (very nice)and down past Grouse Lake into Pine Valley. Grouse lake has an ok sandy swimming spot, but it's not as nice as Gem or Buck.
The conditions were very dry and we were kicking up a lot of dust on our way out.