I've been. It's pretty decent, however LOTS of hardware (which is almost all playable, a plus) was broken. I would say 40% of what I tried was faulty in some way. A shame, because they have some really awesome displays. Most notable are:
Lots of Parappa the Rapper merch, US, UK, Japan all represented
Freeplay Arcade - DK, Missile Command, Galaga, the usual suspects, Vectorbeam's SPACE WAR
Playable Famicom 3D Glasses, Neo Geo AES, Jaguar, Japanese Turbografx-16 and Dreamcast games
10 Player Saturn Bomberman - this was awesome to have 9 other people to play with for once
Computer Space, the one player and two player models on display (no touching!). The two player model was turned on
Original Miyamoto 'Jumpman' sketches
+tons more
I had fun, well worth a day and $12. Anyone from the Portland/Metro area should check this out.