The Flex is sharing the powertrain with several other Ford models and all are doing well. Models with AWD made before a certain date were having issues with the PTO seal, this issue has since been resolved. Ford has built a winner that is far tougher than the current minivans.
We've had our going on a year, and multiple thumbs up! Highly recommended. What tipped us was the towing capcity, 4500 lbs. To be honest, I have not towed with it yet, so no real world reports on that. Rock solid, no repairs, oil changes only.
We traded our 07 Edge SEL+ for an 09 Flex Limited. The wife only has just over 3000 miles on the Flex in almost 4 months, but she has had no issues with it at all.
The biggest complaints I have about the 09 Flex is the lack of being able to select gears, only has drive and first, and no telescopic steering wheel. For 2010 they fix the telescopic steering wheel in all models and the Ecoboost model gets selectable gears via. steering wheel shift padels.
We are getting better then expected MPG. Our Edge, we traded, got 22-23 on the hiway, but the Flex is getting 24-25+ mpg. We drove from Central Iowa to Denver and got 25.4 mpg on the way out and 25.2 on the way back, and that was going 79 mph (gps).
I have towed 2000# with the Flex for about 100 miles and didn't even know it was back there. If you get the trailer tow package you get the class III hitch, 4 pin and 7 pin wiring harnesses and engine and tranny coolers. And if you do need to hook up trailer brake controler the wires are already under the dash.
The Expy will have a little more interior room, but the Flex is much easier to drive, park, and everyday live with. I also give our Flex multiple thumbs up. I wish we would have waited for the Ecoboost engine, but the natrual 3.5 does good and has enough power for 99% of the time. Plus if the Flex had more power I would be using it and would probably be getting a lot worse MPG.