We stayed in Boom's Cafe for four nights during Fullmoon Party time in a Fan Bungalow (400 B per night) right on the beach and we had a really good time.
Nok the owner is very lovely and speaks Thai, English and German very well. She has 6 very cute dogs that run around the place all the time and behave well (f.ex. they do not go onto or into the bungalows!). If you need a taxi or have other wishes just ask her, she is going to help you for sure!
There is a small restaurant with a "book-change-area", where you can also have free WIFI. We ate there all the time - Nok is cooking for you, whenever you're hungry! She is a very good cook. Also try the coconut and banana milkshake :)
Our fan bungalow - right on the beach - was very clean with a big bathroom (you also get bedsheets and toilet paper) and had a hammock.
The beach is beautiful and there are only the few guests from Boom's Cafe staying there! It's a very quiet place - near but far enough away from loud Haad Rin, with the best sunsets we saw on our whole trip. Unfortunately the sea is very flat (you cannot swim there) - but that's normal for the southcoast of Koh Phangan.
To Fullmoon Party we walked down the beach to Haad Rin. It's about a 45 Min walk - very rocky. Back we took a taxi (100 B per person) and it took only 10 Min.
So if you are going to Koh Phangan, stay at this beautiful place, relax and enjoy the silence!