I owned a 2016 WRX that I bought new in March 2016 and kept for 3 years and >40,000 miles. I took it out to the mountains (Deal's Gap - otherwise known as the Tail of the Dragon - Hwy. 129 in East Tennessee) regularly and beat on it. It took all that abuse in stride. Never even used any measurable oil between changes. The only issue it had was that the brakes were inadequate for that kind of use, which was really very close to spending the day at the track. Subaru has since rectified that issue - for either 2019 or 2020, they started putting 2-piece brake rotors on the WRX, which should help the warping problem I had with mine.
As far as the dealer and Subaru of America - I had great service from them. The car started making a noise a few months after I bought it, and spent weeks at the dealership with them trying to diagnose it. I got SOA involved, they sent a troubleshooter out, and found an exhaust manifold stud nut missing, which had resulted in the gasket being eroded through and leaking, causing a whistle at high RPM.
For my trouble, SOA hooked me up with a fully transferable, 7-year, 100,000-mile Gold Extended Service Plan, free. In addition to that, the dealer always gave me a loaner car when the WRX was in for service.
I ended up selling the car to save some money, primarily, because it was a weekend car for me, and I have a truck that's paid for. I really liked it, and would strongly consider owning one of the next-generation WRXs in the future - especially if they bring back the hatchback body style.
The only other issue I had with the car was how it was tuned from the factory. It had pretty bad rev hang, laggy response from the drive-by-wire throttle, and just bad accelerator tuning overall. Throttle tuning on the cars is not linear; pressing the pedal down 25% of its travel yields, in my estimation, 75% throttle opening, or more. I've heard that the Cobb Accessport ECU re-flash device, which is similar to the KTuner device I just ordered for the wife's Civic 1.5T, fixes that problem. But, like OppositeLock was saying, lots of people start having issues with the WRXs after they start tuning them and cranking up the boost. I don't think a mild tune would hurt anything on the WRX, but, lots of guys (younger guys in particular) go hog wild and do full bolt-ons and turn the boost way up, and that's where they run into problems. The FA20DIT is rated at 268 HP/258 LB-FT, and the connecting rods, especially, can't take an extra 150 LB-FT at 2000 RPM.
I think my favorite part about the car was the handling. The steering, even though it was electric-assist, was wonderful, and the car handled just superbly. Easy to drive, and the bias towards understeer and the AWD made it a very safe car. It was hard to get yourself into trouble pushing too hard.