My mom and I rented deluxe tubes (equipped with bottom, head rest and cup holder) and took the 1.5 trip. I LOVE that your tube trip ends where your car is parked, rather than being bussed back.
We shared a bus ride with a large group of 20 somethings, all with beer in hand. The bus ride was rough, loud and dusty, but short. The bus driver loaned us a piece of rope (I recommend bringing your own in case they don't have any) so we could tie together. The trip was under the estimated time, and I could've gone for at least another hour. Take your time, stop along the way, and bring some beverages. The next trip up from 1.5 hours is 5 hours and the young man helping us disembark mentioned that many people who do that long of a trip are MORE than ready for it to be over.
The water is gently flowing, it's not too deep and would be a good ride for a first time. There is a lot of vacant land along and so it's peaceful. There were a few kids that had a home along the bank about halfway between who were collecting bottles. I don't know how frequently they are out, but keep your empties handy for them. Also, get a tube with a bottom because the water is so shallow, you will be running over branches and rocks that you'll scrape yourself on. There aren't any bathrooms on this trip, so plan accordingly. Don't forget you'll have to take your car key.