I took the Riverside Shuttle from Nairobi Airport to Arusha recently. I booked in advance over their website and paid by credit card.
As promised there was someone to meet me at the airport and escort me to the waiting/rendevous area.
First I was taken by a shuttle bus, together with clients of the competitor, to a gas station 10/15 minutes away from the airport to await the bus coming from Nairobi city.
When the bus arrived it was full. I was given a folding jump seat in the aisle, extremly uncomfortable and without any support whatsoever for the upper back and neck in an emergency situation.The other seats were high enough to offer such protection.
I filed a complaint by email with Riverside, at the first opportunity. It turned out that the website is not run by Riverside at all, but by a Kilimanjaro trekking company in Wales. They forwarded my complaint, and request for at least a partial refund to Riverside, but when the reply finally came back, denying my claim, The booking agency washed their hands of the whole matter.
Anyone who joins the bus at Nairobi airport will run this same risk. You have NO idea of the passenger load until it is too late to make alternative arrangements. If you were taking the morning departure, you could perhaps wait until the afternoon one, but, if like me, you are taking the afternoon shuttle, the only possible alternative is to overnight in Nairobi and try the following day, which quite possibly is not an option because of other arrangements, as was my case.
I do not mind paying a premium price, which one way $35 is, if everything is as anticipated, but to pay nearly double the price paid locally, AND get an unsafe seat, is too much.
Riverside claimed that all foreigners pay the higher price, but my own research in Arusha disproved this. I was offered a seat at the local price, which means paid locally not just for local residents.
I would warn anyone considering using the Riverside Shuttle with Nairobi Airport as their pick-up point, to get some guarantees in writing from the booking agency before commiting themselves to this service. I would expect that joining in Nairobi city, at the starting point would not enounter this problem.