Overall, we had a good and enjoyable experience. The downhill bike ride had spectacular view, including recommended restaurants and shops to check out along the way.
I gave this review a four due to these two small hick-ups. First, we arrived at Haleakala site a little late (our reservation was in late July - peak season). Many of the spots were filled up but luckily we found a spot anyway. Second, we booked through TripAdvisor but our names did not show up on their reservation system during check-in. A few folks had the same issue as well. This caused a delay for departure from the bike shop, which may be while we arrived late to the final destination. So be sure to call ahead to confirm if you booked through TripAdvisor.
Here are some of the good parts with our experience. [1] Although we had issue with the reservation now on their system, they quickly managed us into the trip. [2] They provided helmets and extra jackets if needed (a lot of people were not well prepared for the 40s up at the top). [3] The bikes are nice and comfortable. [4] Our guide was funny and did his best to entertain sleepy passengers in the early hours during our 1.5-hour ride to the top. He also did a good job at explaining where to turn (in the dark and in reverse since we were going the opposite direction!). He included a lot of fun and trivial facts to help us remember better. [5] We booked the non-guided tour and we could return the bike as late as 4 PM. We were able to stop and check our shops and restaurants along the way. [6] If you have action camera (e.g., GoPro or similar), the helmet have accessories for you to clip on.
Our friend recommended Bike Maui to us and we would recommend them to our friends too. Just use common sense, be careful and have fun!
Caution: The bike ride is not for everyone. If someone in your group is not a strong rider (kids or adults), you may want to assess carefully. The roads have little shoulders, if any, and there are cars periodically. We decided to not let our younger kids (12 and 9) and my wife to do it. It was just my 17-year-old nephew, 15-year-old son and me. We were glad that we made that decision. This is true regardless of whether or not you choose to go with Bike Maui or other companies. They all share the same downhill road for the most part.