I've been there a few times. It's also just down the road from work so even if I'm not there we gather on the roof and can see everything flying overhead :D
it's always been a good experience, last time I was there in 06 I think I got to go on board the A380 prototype filled with water barrels and no seats/bulkheads/etc... as huge inside as a cathedral!
Also spoke to the US Army guys, they're top notch, I asked them very nicely and they let my little brother on board a Blackhawk with them and gave him some unit patches which made his year I think
They also had the V22 Osprey there, first time I'd ever seen it and it had the weirdest takeoff ever, but what a brilliant and strange plane/helicopter thing.
It's a good day.