We host a DCI show at our school. We have for the past 32 years. At least one corp stays at our school every year and rehearses all day. This year two stayed at our school (Phantom Regiment and the Mandarins).
It's amazingly awesome, but I've never really sat down as a spectator and watched the show. I'm always working. Our band hosts it, and all the band members/parents work while the show is going on.
I did get to see Phantoms show while they were rehearsing during the day (in 105 degree heat!) and it was pretty awesome. I also saw part of the Blue Devils & Madison Scouts' show, and from what I saw I liked them both.
Needless to say, you'll have an awesome time (if you're into marching).