A small fishing village in the middle of nowhere, and so different from the concrete covered tourist trap that is Cancun, that you might decide you like the Caribbean coast of Mexico after all.
My suggestion:
A lot of people opt to go there for a day trip. That's a mistake! If you stay there for one or two nights you will have the chance to be one with the nature around when when it wakes up (even travellers with limited budgets should find something suitable).
Summary:
Punta Allen is magical, but you will have to earn your arrival at this little corner of paradise. To get there you have to travel a chaotic 50 kilometres from Tulum, finishing up on a narrow dirt road where you will find the village.