First of all there's a big difference in how Android gets upgraded. Google doesn't need to upgrade the base operating system in order to push changes to its apps and they can even push security fixes and upgrades to the base operating system by means of Play Services and supporting libraries by which they push backports.

It also depends on the Android device. I have a Nexus 6, released 2014, that's on the latest Android 7 (Nougat) and my old Nexus 4, released 2012, is on Android 5 (Lollipop).

Maybe I would have preferred if my Nexus 4 also got upgraded to the latest, but then again it might not have the needed juice, I like very much how it runs right now and all the apps I use still work and receive updates. And I also have an older iPad that got upgraded by Apple and is now unusable.

Even so, with Apple there's no way out - once upgraded, it stays upgraded and once support is dropped, it stays droppped. With my Nexus I have a choice - because of Android's nature I can always use CyanogenMod. It's not exactly a solution for the non-technical-savvy, but it works.

My Note 4 came with kitkat installed two years ago. Shortly thereafter I was able to upgrade to lollipop. For the past several months now I've been ignoring the available upgrade to marshmallow because honestly neither my cell provider nor Google has any incentive to let me keep a perfectly good phone for another year or two, so I'm worried a major performance hit is the only real feature I can expect from the new version. I know I'm being slightly irrational in this concern, but can anyone confirm that the jump from Android 5 to 6 doesn't cripple phones with "old" specs (since it's targeted to the latest phones)? I'd love to update if it turns out this is not the case.

5 to 6 was fine on my G4. I'm not sure how it compares to the Note 4 but the phone is at least a generation old. There is another pending OS update I've been ignoring for a few months, not for fear of being crippled, but just because I can.

Ditto 4.4