I had a Flex. They look nice, but have some significant flaws: For one, they’re notorious for eating wheelbearings. I bought mine with about 60k on the odometer, and had to replace three of the four, and one had to be done again within 7000 miles. It’s a heavy car, so it really stresses the driveline. It also has a habit of warping brake rotors for the same reason (weight). The non-Ecoboost engine (standard option) is sluggish due to pushing all that weight. Road noise is an issue even with the smallest-diameter wheels, and I suspect the “premium” wheels would make the car sound like a skateboard. Despite the size, they’re somewhat cramped inside. If you opt for the all-wheel-drive option, you have to be meticulous with maintenance. The “transfer case” holds barely a pint of oil, and has a nasty habit of losing seals, so you either evacuate all that oil onto the highway, or worse, into the transmission where you don’t know it happened.
On the plus side, it’s a great car if you live fairly near a city. It’s great on “good” roads, and with the AWD it’s quite sure-footed in snow. Gas mileage is tolerable; I saw around 18-19 in mixed driving, and managed 20-21 in mostly-highway usage. The gas tank capacity is small for an almost-SUV though, only 15 gallons, and it’s split into two 7-gallon saddle tanks (and there are reports of the transfer system failing, so you only get 7gal of use out of it before your “low fuel” light comes on).
I forgot to mention also that the Flex has a design issue, where the plastic tray under the wiper area seems almost engineered to direct leaves and other debris down inside the front fenders, where it collects, holds moisture and promotes rot.