Some buddies of mine went about a month ago for the first time and have been back twice since. They were on quads but said there were a few bikes there and a few trails to poke around on if sand wasn't working out for you. They seem to think its worth it.
I went a year ago and failed to purchase a paddle tire. Fortunately, I had just put on a new 756 (?) and my bike still flew. I could easily outrun all of the four wheelers at the drag section. Although, a paddle tire would still have helped. You can rent paddle tires there too, if I remember right. Be prepared to roast though! It's hot in the summer! We went right after Memorial Day and froze, it was the strangest thing! There are trails ( I don't recall any without sand though) but the best riding is on the dunes. If you like to jump, it's a blast. If you have a headlight and tailight, you can ride at night and there is nothing wickeder (is that a word?)! Don't try to fake it! I had a headlight, but no tailight. So, I taped a redlens flashlight onto my fender and they caught it. Bummer. But, I went down the street, bought a trailer tail light, destroyed an extension cord for the wire and bent an adjustable exhaust disk from my buddys quad and mounted a makeshift tail light. It was fine with that and they let me ride. You will have to buy a whip there though. They are fairly cheap. Get one with the warranty because you will break them. The local shops will offer whips at a low price and ones that cost a couple of dollars more for the warranty. Get them. I went through 4 whips in two days. I only had to pay for one. They have a little bracket that mounts between your rear axle bolt and the swingarm. drilled two small holes in my rear fender and ziptied the whip up there to keep it from hitting me in the back. My suspension compressed so much though that my fender will slowly eat away at the whip until the whip broke. That's why I went through so many. It's kinda expensive to ride and camp there. If you have friends, you can all share a campsite and split the cost. But, they'll still charge every automobile in the campsite though. I parked my truck in town and rode in with my buddy. We split the cost. If you carpool, you really cut down on the cost. The burger joint at the end of the camping area is pretty good! Good food, good price. Oh yeah, be careful when coming to the top of a dune! My buddies wife broke her shoulder blade a couple of months back. If the wind is blowing steady and hard from one direction, it'll carve bluffs onto the upwind sides of the dunes. She didn't know this and toppled off a 20 foot bluff on a quad. Look before you leap! The sand doesn't hurt near as bad as a rocky trail or hard pack track! It's like landing on a pillow! It really helps your confidence! Also, when you land from a jump, be hard on the gas! If you aren't on the gas, the sand will grab your tires and your momentum will throw you over the bars. Been there done that! If you are jumping, try and have a friend stay atop the dune so as to alert other riders that you are coming over and to prevent them from riding through your landing area. Never seen it, but have heard horror stories.
You've got to go! At least once! It was an incredible experience and I hope to get to do it again someday! It was a little over 5 hours for me from Fayetteville, Arkansas. I don't know why I didn't go back while I was still living there! Let us know how it goes!