I was staying in Samui for 4 months and needed a bungalow to fit my budget. Lemon tree has bungalows for longer stay and also just for few nights. I think all the bungalows differ a bit, so I would check your bungalow with the owners first so you don't get disappointed. Despite some earlier reviews stating the owners are crazy I have to say just the opposite. They are very friendly and have helped me with all my needs.
You have to understand that this is not a 4 star hotel in Lamai or Chaweng. You either need to have a motorcycle or money to pay for a taxi, since the location is quite remote. Not all the bungalows have flat screen TVs and a full kitchen. I think the price is very reasonable and reflects all this. I would not come here just for a 2 week holiday, but I would definitely recommend this for base for a longer trip.
Only negative thing I can think of are the roosters croaking in the neighbour's yard. It took me a week to get used to this and have a good night sleep