Our extended family (8 people + dog) stayed here for a week in July and really enjoyed it, despite the lack of AC during a heat wave. It was easy to kayak the lake, we could all eat dinner on the deck, we made s'mores around the fire pit, and the kids loved all the toys and games (plus the badminton net and hammock). I would definitely recommend it, but renters should be aware of a couple of things:
1. There's no Internet, and while the owner said AT&T cell service is excellent, we got virtually no signal with our Verizon or T-Mobile devices. (This was a challenge for me personally, because I had to work part of the week and was hoping to set up a mobile hotspot. But the adorable town of Great Barrington is very close by, with free Wi-Fi in the library.)
2. It's a pretty rustic and natural setting, which was a plus for some of us but not for everyone. We saw a number of beavers -- legit! -- swimming in the lake, which was really cool. We also saw a water snake near the dock, which was not as cool, and pretty much kept us from swimming the rest of the week!
If you don't mind getting up close and personal with nature, and are more interested in kayaking than swimming (or visit in the winter instead) then it's a really nice, cozy, pet-friendly place for a big group.