I've got a 2013 Sport Premium. I don't know if i'm being paranoid, but when it's quiet enough to really listen to the engine, I can hear what I can described as a slight rattling. It's kind of like a higher pitched rev sound when accelerating, pretty much undetectable while coasting or idling.
It's quite possible that it's nothing and it's simply me learning to focus more on the sounds my engine makes, as this is my first boxer engine and first subie (coming from a jetta).
I've heard about the piston slap of boxer engines but I'm not sure if that's what i'm hearing. The car only has 4000 miles on it and the dealer told me not to bother with my first oil change until 7500ish.