I spent 4 days in Provincetown by myself in September/October 2005 and had a really great time! I took a ferry to P'town from Boston, which was AWFUL because of rough seas. They passed out barf bags and it was quite a horrifying and uncomfortable experience!
The best thing was the cottage I rented on Commercial Street (Aerie House & Beach Club). It was a cute little cottage with a sleeping loft where I had to climb a ladder to go to bed! And a great deck overlooking the harbor, which was awesome for stargazing late at night. My guesthouse had bike rentals for free, so I took a ride out to the dunes and ocean beaches (Herring Cove and Race Point)--it was fun but extremely tiring with all the hills (it made me realize how out of shape I am!).
I went out every night. The bars were kind of slow because it was off-season, but I really enjoyed the A House (a gay bar). There were extremely friendly locals, and it was very easy to talk to people on the smoking patios. It's probably one of the friendliest places I've ever been! There is lots of good shopping in Provincetown--I bought lots of unique gifts for friends and family. I had to take a little puddle-jumper plane back to Boston because the ferries weren't running. I can't wait to go again! It was just so great strolling up and down Commercial Street. And I really loved the off-season. I got lucky with the weather, even though in was the end of September/beginning of October.
Quick Tips:
If you are relying on the ferries for transportation to Provincetown, make sure you call them to verify the schedules. Luckily, I checked the day before I left and found out that they stopped running in the morning during my stay there, so I had to fly home. Bring lots of money, as there is great shopping! Be careful where you stay--I heard a lot of people complaining about their accommodations (although I loved mine). Bars close early (1am), which is normally when we're getting STARTED here in Chicago!
Best Way To Get Around:
Traffic seemed awful, so park your car and walk or rent a bike.