Regardless of the 14 day period from Apple, if in a few weeks there hasn't been a software fix am I right to think that you could still go to an Apple Store and request an exchange?
You can request it all you want. But Apple
could take the position that "+/- 5 degrees is normal operation" and refuse an exchange because your device is "within tolerances" (because, after all, THEY specify the acceptable tolerances for their product). Or, they could decide to just keep telling people "the problem is software, an update will be coming eventually, so our policy is not to exchange for compass/level errors."
So if the inaccurate orientation is a "deal-breaker" for you, and you are within the 14 days, the safest route would be a return. Of course that assumes there is some other phone out there that has the feature set you need and doesn't have any "deal-breaker" malfunctions of its own.
Personally, I am keeping mine. The orientation problem IS a big issue for me (particularly in astronomy apps), but I like everything else about the phone. And I expect there will be some sort of resolution -- if not from Apple, then from app developers who will start adding their own calibration routines to apps that need it. I would prefer a fix from Apple, rather than having to calibrate every individual app using multiple developers' procedures, but if Apple doesn't step up then I expect developers will.
Of course with the exception of the few folks here that have time-travelled to the future and returned, nobody knows how this will play out.