Mainly, the stuff I'm looking to buy at GenCon falls into one of two categories:
- stuff that's not at the FLGS yet, and
- stuff that's too old for the FLGS to carry
I generally spend at least a half-hour each GenCon combing through the bookshelves at a vendor, whose name I can't remember, but festoons the shelves with signs exclaiming "Buy 1, Get 3 Free" -- it's a good way to find those out-of-print RPG books that'll help inspire your next dungeon or other project.
Also purchased older boxes of D&D Miniatures that haven't been in the FLGS since 2010.
This year, I'm hoping to visit one of the board game vendors and see if I can find a copy of SPI's "Freedom in the Galaxy", and also an original Star Fleet Battles boxed game with counters. I might be able to find those sorts of things on e-Bay, but I feel better being able to see and handle the thing I'm looking to buy rather than relying on photos.
Just my $0.02US.