I meant to post this a few months ago, as I travelled to Havana and Varadero in January of this year and booked my transfers and hotels through vacacionartravel.com - a Cuban based travel agency. We didn't need airfare as I was flying on Air Canada with Aeroplan points.
I was concerned about using this site as I couldn't find many reviews and they require credit card information up front and you just print out vouchers from your computer to use for the transfers and hotel accommodation when you get there.
I just want to report that I had a wonderful experience with this company. They charged my credit card what they said they would charge (in Euro's through a Paris location) and we had no problems with any of the three hotel reservations and 2 transfer bookings that we made.
In fact.... we had made a reservation at the Tryp Peninsula in Varadero and when we arrived found out that the hotel was oversold. I was not impressed, but it turned out so well. They moved us to the property next door (Paridisus Princessa Del Mar) and it was MUCH NICER than the accommodation we had booked and paid for.
A very positive experience... if anyone has questions, feel free to contact me.