I realize it'll be a few weeks/months before we see full blown reviews of this watch. Looking forward especially from Youtube fitness bloggers. That said, a couple of general questions. Altimeter. I understand this helps with activities such as stair climbing or mountain climbing. I assume this would this help with accuracy for running elevations as well? Improved Heart rate monitor. Is this a physical change in the Series 3, or simply a Watch OS4 software upgrade that would apply to older Series 2 watches too?