'less' is sometimes 'more' - unless you're in OS design...
I ditched BBC Micro's 'round 1990 something, ditched NT4 years after, then moved to Linux proper in 1997, and, whether it's my memory failing, i'm not sure, but i don't remember many OS 'updates' ever really making the hardware seem better..
I had my fill of overheating laptops, i (foolishly) bought a brand new 17" Packard Bell, and the design was so poor that it overheated installing almost any linux distro, and it shut down, so i had to install linux with the laptop on it's side and a house fan blowing cool air in, underneath, then i could install decent power management once the OS was in, i soon got fed up of that, and the flimsy keyboard which failed three times in the first year, so I bought a Macbook Pro 15 round about 2009 instead and i never looked back, it ran Linux better than the generic black plastic laptops, Apple hardware was good, Snow Leopard was great, and so my music production was moved to OS X, and i moved fully to Macs and now have iMacs and 2 Macbooks,
As for upgrades, well, If a garage 'updated' my car, and it came back with fuel efficiency down, the radiator constantly boiling over and it took an age to start, and it drove slower, but, on the plus side, did come back with shiny new stereo ashtrays, new seat covers and minimally upgraded steering lock, many of us wouldn't call it much of an upgrade..
But here in computer world, it doesn't quite work that way, almost every OS update seems to make the device slower, hotter, and more power hungry, in what world is that an update ? i've even noticed this on an Android device too, as well as all three major OS's over the years. I smell a rat.
I think Yosemite is noticably slower than Snow Leopard, and Apples' lack of security patches for anything a few years old stinks, thus making Snow Leopard insecure and unable to run current software, (where ironically, Windows on the old Mac would give you all the newest software on there, Linux too) forcing users who can't move OS to then run a insecure OS or jump ship.
Yosemite soon won't get any love either, and will be doomed too, s but is about as far current as i will probably go, I'm not happy with El Capitan, as it is more restricted, and Sierra will be worse still, i have no interest in running either.
Unless Apple get their **** together, my internet connected iMacs and Macbooks will be then running BSD or Linux, and i'll say 'it was nice while it lasted Apple, thanks for all the hardware' and i'll move on to an OS that isn't going to screw me as often, Apple won't miss me, and i won't miss Apple.