Pros:
I love this course. I've played Flat Rock a bunch of times over the years, and I enjoy it more every time. Sean owns the property, and is the nicest guy you could hope the meet.
So, before you even start play, you have a fantastic little setup. Barn with disc golf memorabilia, a small pro shop, a gorgeous deck with Adirondack chairs for pre/post round beers.
Then you get to actually start playing, and the course is just a blast to play. Challenging, but mostly fair. Great mix of shots, forehand/backhand, open bombs, tight drives, etc. Lots of personality on the course with little sculptures and decorations scattered around. Beautiful property with several little creeks running through it, and a pond that comes into play on 2 holes.
Cons:
So...I really don't like hole 2. There's challenging, and then there's, "Wait...I need to do what?" Walk the hole before you drive. The tee sign gives a basic idea, but you'll want to check out the lines you need.
It can get pretty mucky there in spring time/wet weather. The bugs can be brutal in the summer, so make sure to pack some bug spray.
Other Thoughts:
I live a little over an hour from the course, so I don't get to play it as often as I'd like. It is absolutely worth the drive though. $8 to play all day is a great deal for a course a course like this. Or, make a full Disc Golf day of it, and also check out Tully Lake about 20 minutes away.
If you have the chance, try to play a tournament here. Amazing time.