I stayed at Rung Arun a few months ago and loved it. It was one of those places that I say to myself "I'll take the time to give them a great review when I get home", and then I get lazy and never do. But this time I am because they really helped me out.
After months of travel I realized I left a memory card with many weeks of pics somewhere. I emailed Rung Arun and they got back to me saying they had found a card. They have now mailed it back to Canada, and have not charged me a penny, even though I've tried to pay for their troubles and mailing costs.
The other reviews will tell you why to stay here (great beach, amazing people, good food), so I'll leave mine at that.. they are genuinely great people that will go the extra mile, even after you've stayed there.

Stayed here for 7 nights in Koh Phangon, for the Full Moon party. We booked online as we were worried about availability of things for the full moon. The resort was empty for the first few days though until the full moon party. The resort is quiet and relaxing... Very clean and has a great spot on the beach. The couple who run Rung Arun are very nice, and extremely helpful.
If you are looking for somewhere a bit more lively the resort next along on the beach is very lively, and does an amazing BBQ in th evenings. Having said that you can't hear the loud music from Rung Arun - which is good if you like your sleep! There are lots of cats and dogs on this resort, but they are very freindly!
I would come back here again, despite it being a little too far away from Had Rin or any shops... This is fine of you hire a motor bike, but if not, then expect to pay 50-100 baht to get into Thong Sala.

My fiancée and I originally planned to only stay a few nights at the Rung Arun to use the resort as a relaxing base for before and after the full moon party. However, we fell in love with the Rung Arun from the first moment we arrived and ended up staying a total of nine nights. The resort is owned and run by a very friendly Thai couple and a handful of staff, giving the place a relaxed family feel that we just never wanted to leave. The bungalows are superb value for money, with air-conditioning, a fridge, safety-deposit box, and bath/shower and the whole resort is spotlessly clean. The actual location of the resort is on the edge of Ban Tai so the local area is fairly quiet, but the livelier Thong Sala and Haad Rin are only a short cab ride away. Apart from resort restaurant (which does excellent food) there is also a slightly livelier beach bar & restaurant next door which does a very good BBQ every night on the beach. Cannot recommend this resort enough & we would love to go back!

we went there during first week of september. Since it was the low season, the entire property had only 2 sets of people. First of all the property is located along the nice Ban-Tai stretch and faces the beach. There is a nice pool and wonderfully decorated restaurent. Place is populated by lazy cats and friendly dogs. Since we were vegetarians, the landlady cooked us a delicious vegetarian meal. They were immensely friendly . Next day, we got taxi rides at fair prices, amazing breakfast, and advice on where to head on the island.
This place is near perfect on the wonderful pictueresque island. Prices are dirt cheap, rooms have everything conceivable (AC, hot water), excellent settings (Beach facing, swimming pool) and to top it all - outstanding set of people as owners (cook excellent meals and terribly honest).

I still have excellent memories of this place and would surely come again.