Poking around under the hood of my new WRX I noticed that you can see a little bit of the air filter though the engine side of the air box cover. I opened it up and everything does appear to be sealed (i.e. there's no air gap AFAICT). I've never noticed this before on other cars, but then I've never had a car where the air box was on its side with a vertical opening. Also seems weird that the filter doesn't have a rubber edge, but what do I know?
I just wanted to check w/ other owners to see whether they're all like this, for peace of mind.
Pic (I think it looks worse than it is -- like I said there's no actual gap, neither side of the air box will move if I try to squeeze them together):