All of the above are true. our cllub hosts one each year.I have bought and sold alike. last year I had over 50 frags to sell. I put them all in ziploc baggies and sold them with photo's. this way they were prebagged and sold well. I have also done a frag tank with them. as a seller this was a hassle for me, but those with nice frag tanks will have this type of setup and will either bag it or put it in a container. best advice I can give is bring extra money, and have a target list of what you want. if you see it, BUY it, cause it wont be there when you come back. Last year, I had 3 corals I wanted. I got all three because I had a target list.
on a side note, most individuals selling frags dont want to take them home ( i didnt) so there will be lots of end of the day deals. however, many of these arent the most sought after pieces and while they can be had for cheap, they arent necessarily the "cream of the crop". hence the hit list and the extra cash so you get the best of both ends of the swap! Incidentally, ours in Nashville, TN historically has over 500 attendees. we have several high dollar raffle items and door prizes. you can see the flier in teh announcement section for more information.
There will be commercial sellers with tons of PRIMO frags and individual sellers with home grown and local strains of corals. Both are great, just make sure you know what you are getting and DIP THEM BEFORE INTRODUCTION TO YOUR TANK. last thing you want is AEFW or Red bugs, but 90% of what you will get will be good.
Bring a cooler to store your goodies in! I bring 2 rolling igloo coolers!