First, I want to preface the review with a word about the Cape: Once you accept the simple premise that Cape Code is over-priced, you realize that everything about Green Harbor Resort is 4-start, or "very good". Expensive, yes. But that's just the Cape.
The resort was completely full this weekend, in spite of the high prices. So the hotel is definitely not over-priced in the Cape market. It's just a high-end market. Everything here is pricy and it's been the case for decades.
About is the hotel:
1. The Outstanding
(A) The pool. This is the resort's secret weapon. It's a nice, big, clean 30ft x 50ft outdoor pool and it's delightfully heated to about 85 degrees. We had absolutely dreadful weather this weekend. While most other resorts either don't have pools, or they're not heated, at Green Harbor, I was able to get my fix of water in spite of a terribly cold, windy and rainy weekend thanks to this magnificent pool.
(B) The service: Great. People were polite and welcoming. We got to speak with a number of people at reception and on the grounds. Everyone was very professional and kind. Our many requests (late checkout, pool towels, etc) was met with utmost professionalism and our room was cleaned daily.
(C) The online booking service: Worked perfectly well. And their deposit and cancellation policy is very reasonable.
2. The very good
Our cottage had everything we needed: Comfortable bed, clean sheets, a quiet environment, very well kept grounds and a clothes-line. We had fully functioning A/C, and free, powerful in-room wifi. The bathroom was spotless and we got plenty of towels, soap and shampoo. You also get a fridge, microwave and a grill outside. Given the beach clientele the resort caters to, I wasn't surprised that there was no iron / ironing board. But it would have been nice, given that we had an event to go to. The carpet was a little older, but nothing I would call home to complain about. Given the last two items, the resort gets four stars instead of five. Overall, very good.
3. The so-so
I cannot fault the resort for this, it's just where they are located. But the beach may be disappointing to some. Keep in mind that the hotel sits on a bay near Hyannis, next to a canal. So you get no surf, green water (hence the name) that's somewhat silty. You also have seaweed. The sand part looks artificial. There's nothing wrong with it (the water is warm, and clean). But I suspect that you can have a much more authentic beach experience elsewhere on the Cape.
So to conclude: if you are set in staying in Hyannis, this is definitely the place. If you are seeking a true beach experience, look for hotels further west. If Green Harbor is too steep for your budget, then don't bother with the Cape. My suggestion would be to look at hotels or rentals in Southern Rhode Island. You can have a much better beach experience, with better water, better food, less traffic, less chi-chi, at a fraction of the price. From Boston it would be an extra 100 miles or so. But the value for money doesn't compare. It just won't be "the Cape".