I purchased the Core 9-person extended dome tent for family use during car camping trips. I have several tents including an ultra light 2-person for backpacking, as well as a 4-person and 6-person dome tents for car camping. I've found that for car camping, it is best to take the rated size of a tent and divide it in half to arrive at the right size for comfortably fitting your family. My family of 4 found the Core 9-person tent a nice fit during our first use in the Sierra Mountains near Yosemite.
I considered several 9 and 10-person tents including cabin-style models from various brands, but opted for Core's modified dome tent with extended side areas. I found this design to be more resistant to high winds that you often encounter in the mountains, especially when temperatures fluctuate at sunup or sundown. During our first use, our tent held up to such winds while cabin-style 10-person tents on sites near ours were heavily buffeted. Another key difference is the size and configuration of the rain fly for a dome tent versus a cabin-style tent. The rain flys on cabin-style tents leave a lot more of the tent exposed.
In terms of interior space, we were able to fit two Coleman cots and two twin-size air mattresses into the tent. This left just enough space to maneuver in between, as well as at top and bottom to get in or out of the tent. Next time we are going to swap the air mattresses for two more cots because they have smaller footprints and enable storage of packs underneath. Doing so will open up a lot more space and make the Core tent perfect for our use case. Headroom was adequate for me (6' tall) to stand straight in the middle and slightly stooped at the outer ends. My wife and children could stand comfortably throughout.
While some reviewers had issues with the fabric thickness, I found it consistent with most other tents in terms of strength and weight. Overall the materials and build quality of the tent, fly, screen windows, and zippers were very good.
As for ease of use, the Core 9-person tent is not a one-person setup tent. It uses individual poles with female ends that are connected to male pegs at points along the bottom edge of the tent. This is in contrast to some other tents that use pre-connected poles that are supposed to simplify setup. I point this out because I tried a Coleman 10-person tent with pre-connected poles and found the bulky plastic connection points susceptible to tearing away from the tent, rendering the tent useless. In fact, the first one I tried came with one of the connectors "pre-ripped" from the tent.
Setup and tear down of the Core 9-person tent was quick and very simple but you will need two people. The tent uses four individual poles – two very long and two a bit shorter. The two long poles crisscross the center of the tent to hold up the central dome. After slipping the long poles through the sleeves on top of the tent, the second person should hold up them up while you slip the pole ends over the related pegs at the bottom edges of the tent. The other two poles support the extended side sections of the tent and can be added by just one person. Due to the size of the tent, a second person also comes in handy when putting the fly over the top.
I recommend always putting down a tent footprint underneath your tent to mitigate moisture wicking from the ground and to protect your tent floor. A footprint should be a few inches smaller in length and width than your tent. This is to allow rain to run off the tent and not be captured by the footprint where it could seep under the tent. I typically use a plastic tarp for this purpose, but opted to give Core's footprint (sold separately) a try. It was more expensive than a generic tarp, but it was specified for this tent and it was a good fit and saved some time during setup, it might be worth it. Unfortunately, while the footprint's length was perfect, it was two wide (front to back) for the 9-person tent. As such, I had to fold the excess material under the tent and could not peg it.
Note to Core: While I had no problems with the poles during my first use, due to their long length and the amount of flex necessary to setup and support the tent, it would be helpful if you offered replacement poles as an add-on. Nothing ruins a camping trip like a broken tent and being able to bring along a spare long and short pole would mitigate that issue. Since no such poles were available, I opted to bring along a $4 pole repair kit instead.
All in all, I recommend the Core 9-person extended dome tent. It is a quality tent that sets up easily, has big windows and a bottom vent to regulate temperature, and an ample fly to keep you dry. Unless you want to sleep shoulder to shoulder, don't try cramming the rated 9 people inside. But for 4 or 5 people, this tent is a winner.