What have I given up? Like everyone else, lots of sleep (back in 2001 I actually had lots of trouble sleeping because of the stress from FIRST). Probably a couple thousand dollars spread out over 7 years. I've also lost a number of opportunities for various events. I missed a career fair at school one year because I was at a FIRST Regional (which limited my coop opportunities). I know I've missed skiing several times because of FIRST.
I'm sure I've missed other things but I tend to concentrate on what I've gained because of FIRST: lots of experience, knowledge of engineering outside my speciality, and finally lots of friends.
Matt