First and foremost, Neptune's Villa is a great bargain. We had an ocean view room with a huge balcony during the Full Moon Festival in peak season for about $100 per night, for 2 nights. For contrast, the fancy resorts cost upwards of $800 per night with a 5 night minimum. The pool area was nice, the restaurant served decent food, and the property is right off the beach and a pleasant 10 - 15 minute walk to the Full Moon Festival. Awesome.
Some of the negatives to be aware of:
* The hot water heater in the shower didn't work the entire time we were there, so it was cold showers the whole time. I didn't really mind because the AC didn't really work so the room was sweltering hot, but my wife wasn't happy about it.
* The AC was pretty ineffective, and since they require that it be completely off when you're not in the room it was never really a comfortable temperature.
* Staff weren't particularly friendly, and didn't go out of their way to help. That's fine - it's a great bargain so you shouldn't expect a lot in that department - however it bit us in the ass because we asked, on check-in, for them to arrange for a taxi for us on check-out to our ferry on the other side of the island. They agreed, and said to be in the lobby at 9am that morning. The cab never arrived, so we ended up having to eat the ferry tickets we'd purchased and buy some on a different boat. Not a catastrophe - we made our flight - but the front desk clerk was completely unsympathetic. So, 3 stars.