My experience had been really good. I have done the whole week of RAGBRAI in 1998, when I still had my road bike, and in 2007 on my Vision. I did one day in 2005, 3 days in 2006 and was supposed to do 2 days in 2008, but was sick only did one day and that was miserable. I didn't get sick until I got to the overnight town I started from in the middle of the night. I should have just went back home, but sucked it up and stuck it out and regretted it.
There are more then one way to do RAGBRAI. What I mean is you can join a charter, go with a club/team, go with the large main group, do your own thing and drive a RV or vehicle towing a camper. How ever you decide to do so in 2010 I recommend being registered. YOu can try and go bandit and a lot of people do, but to be with a charter or the large main group you have to be registered and if you have your own RV/vehicle it is harder to find a place to park it in the overnight towns. I have nothing against the bandits overall as far as I am concerned they should open it up, but being registered just makes it easier to do RAGBRAI.
In regards to registering for RAGBRAI there is a limit of how many registered riders that are allowed. It is up to 8,500 weekly passes and up to 1,500 per day day pass riders. And yes they do sell out of the weekly passes. It is a random lottery system that is used. Unless you are with a guranteed group you are subject to the lottery. I have never seen them run out of the day passes. As I mentioned there are what are called gurantee groups. Most of these are grandfathered in before the lottery started from way back when and unless they do something really stupid they are still a guarantee group. The club I belong to is such a group. One of the newest guarantee groups is the Livestrong team because they are a charity raising money to defeat cancer. I do not know how they became a gurantee group I just understand that they are. I do believe with the guarantee groups there are more then 10,000 registered riders a day, so these groups are not taking the credentials away from someone else who is subject to the lottery.
To train for RAGBRAI I recommend you ride in these conditions as much as possible; wind, tail, cross and strong head winds, rain, heat, humidity and hills. If possible all at the same time in the same day. All of these conditions can and have happened on RAGBRAI in the same day. You need to be ready for it. The ride does not stop nor is it cancelled for bad weather.
RAGBRAI ALWAYS starts on the west side of the state and goes to the east side. It is ALWAYS the last full 7 days of July. It DOES NOT always start or end at a river. When it does start at a river it DOES NOT always start at the Missouri River. It has started further inland from a bordering river. Iowa is actually bordered by 3 rivers not 2. The Mississippi, Missouri and Big Sioux. How ever when we started in Rock Rapids in 2007 it was near a river in that area as we were further inland from the Missouri and Big Sioux Rivers.
You will need money. I recommend at least $500 per person and a credit/debit card of some kind.
You will also need to be used to riding with a large group. Unless you go off of the route you are never alone and there are hundreds of riders around you. You'll need to be used to either listening for riders that call out their intentions, use hand/arm signals and be prepared for riders that do neither. 75% of collisions on RAGBRAI are rider to rider. Draft/pace lines happen on RAGBRAI but are not recommended in a large group on a ride such as RAGBRAI.
Take your cell phone, but leave it off when on the route unless/until you actually need it. It will save the battery. And please don't ride and talk on it at the same time.
If there are 2 important things you should have on your bike during RAGBRAI they are sunblock and baby wipes. Sunblock for obvious reasons and I can not stress using it enough, SPF 30 or greater. Baby wipes because the kybos do not always have toilet paper and you'll likely want to clean your hands too. They also come in handy to clean your hands before you eat, or if you have to do something with your bike, change a tube, fix the chain, etc.
You will have fun. Make sure you stop in the pass through towns and see what the overnight towns have to offer. enjoy the food, music and atmosphere of RAGBRAI. It is truly something to be enjoyed and you will enjoy it all that much more if you're prepared for it.
I hope this helps. For more info go here;
http://www.ragbrai.com/ and here;
http://forums.ragbrai.org/