We were nervous, too, but it worked really well. We did not use the buses because we had a car and I was able to disassemble and reassemble it easily and they let us park close. But I have read that bus drivers are very kind and accomodating. Everyone else we dealt with at resorts, in all the parks, on various rides, and on boats, were wonderful. They never gave us even a hint that we were a problem. They knew just what to do and were kind.
Yes, there are no brakes, but when you release the throttle it brakes. It will stop quickly. In fact, you should release the throttle slowly.
As stated the biggest issue was that people treat you as if you can move like they can, so they often cut in front. My wife just had to be careful, and I ran point often times. But she got use to it after a day and we did fine. It was great to get around the resort and the parks. And we could carry all we wanted in the baskets. Plugged it in each night and it lasted all day.
Again, Disney did a great job in handling the scooter wherever we went.
P.S. We used Walker Mobility and got a very cheap price, $20 a day, because we picked it up. Go to the DISabilities forum and there is a tons of info in a sticky including the approved by Disney rental companies and the companies that DIS'ers recommend.
My wife walked a little bit here and there, and was so glad to have the scooter because we covered so many miles!