Having rented villas with friends nearly every summer since 2003, and almost always being delighted with the homes each time, there is one constant I'd say to be a little wary of, and that's an owner who does not live anywhere near the property. The level of hospitality and caring about guests is almost always diminished in such cases. The owner of this villa lives in mainland Portugal and, although the house is quite lovely, he was entirely unresponsive to concerns we had. He had hired a (VERY friendly, lovely) local young man to look out for us, but the young man was limited in terms of decision making and what he personally could offer. He was as baffled as we were by a stove that didn't quite work, as well as the washing machine one needed a PhD to operate (and some of our group do have advanced degrees, just not in engineering). Eventually one of our group found a technical manual for the machine on the internet, without which we would have never been able to wash our clothes.
We were concerned by the lack of window screens to keep mosquitos out (since we saw some in the house when we arrived) and the owner flat-out refused to address our concerns. We asked (via the local young man) if we could buy fans to keep the mosquitos from landing on us if they were a problem and his only response was that he would not pay for them. As it turned out, the mosquitos were really not much of a problem (at least not in June), but another homeowner might have understood our concern and been reassuring -- this one clearly just didn't want to be bothered.
Hot water worked well most of (but not all of) the time, seeming to have little relation to when/if people had been showering, so the times there was only cold water didn't seem to stem from the hot water being used up.
On the many plus sides, though, it is a very pretty house; the mosquitos were only very minimally annoying in the end; and the location is spectacular, in the middle of the large gorgeous caldera. Just the ride from the airport alone was breathtakingly beautiful. Sete Cidades is a tiny, sleepy little town but has everything you could need (groceries, a few restaurants) and friendly people -- it's a much better place to appreciate the natural beauty of São Miguel than some of the other more crowded towns and villages. There's so much on the island of São Miguel to see and do, all of which were at most an hour and a half drive away but most things were much closer. The beautiful city of Ponta Delgada (where the airport is) is only about 40 minutes away and has much to offer in the way of culture, food and entertainment.
The owners of the "Tea House O Poejo" restaurant just next door to Casa Grande were absolutely lovely and enormously helpful, and they also rent properties nearby. Though their properties are smaller and not nearly as grand as Casa Grande, I would likely rent from them next time I return (and I WILL certainly return -- the Azores are absolutely extraordinarily beautiful and not yet overrun by tourists!!!). Still, for the price and for the size of the house, if you have a big group I would say that Casa Grande had more positives than negatives and I would, with relatively slight reservations, recommend it.