We scheduled round trip transportation from Sangster airport in Montego Bay to Princess Senses - The Mangrove Resort. The price ($180) seemed fair based on booking it about 2 weeks before our trip (we forgot to include it at the time of booking our travel package).
We had a text the day before our arrival stating where we would be picked up after passing through immigration and customs, and were given a contact number to text upon arrival. We had a 5-10 minute wait outside, and then our driver was there. It was a busy Friday afternoon for taxis, etc., so we didn't feel it was a long wait.
The overall drive to the hotel was about 90 minutes, due mainly to heavy traffic near the airport and leaving Montego Bay. Our driver (I'm sorry, I forgot her name) was very friendly and drove safely. It's worth noting that driving in Jamaica seems more aggressive than in the US (specifically the Midwest), but I never felt like were in danger. Different places have different standards. The Toyota van was comfortable, and could probably seat 5 passengers comfortably, so long as the luggage isn't excessive.
When we left the hotel, we contacted the transportation company the day before to confirm our pick-up at the hotel. We gave the flight info, and then a bit later were told what time to expect a pick-up. Again, the ride was on time for pick-up (11am for a 2:45pm flight), and the traffic was a bit lighter on a Wednesday going back to MBJ. It was about 75 minutes to get back, and then about 20 minutes to get through security. All this was with good weather, so if the weather is bad, adjust your expectations probably by at least 30 minutes.
We had the same driver going back, and again she was very friendly, highlighting different things along the road and in the towns.
My only suggestion would be for the transportation company to be more proactive with the pick-up to go back to the airport. I'm guessing I'd have received a text by late Tuesday afternoon to confirm a pick-up to go back, but I was the first to do this, giving my flight info and asking when I could expect a pick-up. Also, it's done via text and not a site, and there wasn't a confirmation number. The idea of getting stranded or having to arrange transportation on a moment's notice wasn't something we wanted, so the proactive part was to give us peace of mind.