Yeah I have. A bunch of Ohio teams head down every year. Team Strikers have attended the event since the very fist one(like 6-7 years ago). For a long time Irene was the pinnacle of airsoft in the US. Now there are allot more games that can easily compete with Irene as far as playability goes.
Irene costs about $200(estimate, depends year to year), you also need to be part of a team, minimum age limit of 18yrs, and have another team who have been to LC games vouch for you.
If you want to see another really good national event, check out the Pine Planes series.
sticks