We did the Tulum Ruins Tour last summer. We loved it and would do it again in a flash. Very soon after docking at Cozumel we took a jet ferry directly from the ship to the mainland. We walked about 1/2 mile through a town area to the bus then rode the bus for an hour or so to Tulum. We stopped on the way for a bathroom break and some shopping. I thought it was very good shopping (scarves, handmade jewelry, etc.) and was able to bargain for some very good prices. Once at Tulum the tour lasts an hour or so -- excellent tour guide, he's of Mayan descent and very proud of his ancestory, very knowledgable. We then had about an hour at the most beautiful (and practically deserted) beach I saw on the whole trip. On the way back they handed out Subway sandwiches and had beer or soda available.
However, I will say that it is the longest of the tours, possibly the priciest. It is also not for young kids - the day can get long and warm and if you don't have some interest in the Mayan culture and a more mature attention span it is probably not the best tour.