Yes, I've entered a few that have won at the state fair. No, it isn't difficult to follow the rules since there are usually so many categories. Just be sure to read them very carefully.
All the pics I had of the quilts were on a comp that got destroyed when our house got struck by lightning, so I no longer have any pics of them :(
I'm currently working on 3 that will be entered in next year's fair.
If you think you'd like to enter something, go for it!