I'd say if you go, its better during a weekday. I went last year during a weekday and it was not packed. Weekends though a lot of people who know nothing about cars go and they bring their kids who touch the cars. There where a couple of scratches on 150k BMW, and it was a sacrilege. Plus they all scramble to get inside.
I was a little bummed out that the trucks where for the most part sealed. Last year you could go inside a f250 or f150 truck, but for some reason, they locked them.
The whole Belgium incident makes getting in a hassle. They definitely increased security. Not that it would help as theres a big crowd waiting by the metal detectors anyways. Eh, but I guess its the illusion of safety that we have to play by.