FBIL & FSIL just returned from their honeymoon here. They absolutely loved it. They rented a jeep from the Cancun airport and drove down to Tulum. They said driving in Mexico wasn't bad at all (thanks to the many speedbumps that makes everyone have to slow down).
They really liked Tulum because it had hardly any signs of being "Americanized".
The guy that owns this little hotel is from Argentina.
FSIL showed me pics yesterday - I'll have to get her to send them to me so I can post them for you. It looks really cute and they said they had a great time and want to go back and buy a house there
Also, Tulum is where the Corona commercials are shot - that's how they found out about it. Just an extra little tid bit.