When I was on Sprint PCS with a Samsung Galaxy SII, Sprint rolled back the Gingerbread update twice and managed to brick a huge amount of subscribers' phones in doing it. Then about a month later, they came out with the "fix" and had to roll that back too. Bricked as many phones as the first time and if you were lucky enough for the Gingerbread OTA distro to be a success (there was no desktop install then, you may recall) then you found that battery life was halved and they apparently gave up completely on trying to get the GPS to acquire a signal.
... and this was the Android 'update' to a version that had already been released by Google for over a year. By the time Sprint PCS finally released Ice Cream Sandwich (updating from Gingerbread) to the Galaxy II, Jelly Bean had already released to new phones six months earlier. I had a phone made in 2011 that was getting an Android OS in late 2012 that was originally released a year earlier.
This phone went from being pretty reliable phone (albeit with flaky and comically-inaccurate GPS) to a self-rebooting power-starved massive POS in just one "upgrade". Go read the historical forums about what an abortion of a phone this turned out to be for Samsung's flagship line, regardless of carrier.
Sprint blamed Samsung. Samsung blamed Google. Google said "That distro has been out for fifteen months already. Blame Sprint and Samsung", and the final reason for the year-plus delay in finally getting an outdated OS on the Galaxy II was both Samsung AND Sprint glurging up the distro with shitheaps of rotten proprietary bloatware that can't be uninstalled. 800mb of lousy car race game to demo the new motion control feature that ended up not working very well at all.
Google releases Android, Samsung shits it up with ching-chong garbage, then hands that off to the service carrier for them to add even more localized proprietary garbage. If it fails QA, it's back to Samsung and then Sprint tries again. Or you can get iPhone and get the new update on the same day everyone else on the planet does.
Sprint attempted to make things right by offering me a brand new two year contract on the new Galaxy III, but I said KMA and got a new iPhone 5 on Verizon. Fact is that whatever Android version you get pre-installed with a new Samsung phone on any carrier is probably the only one you'll ever get. Don't count on any patches, much less updates. If something doesn't work, the solution is for you to "upgrade" to whatever new whizbang Samsung aigoo-phono-san that they have at your local service provider store. Once the new model is out, the old one you have in your hand is dead to them. DEAD.
Maybe some Finnish college student named Rukki Perkelettavi will post a how-to in poor English on how to jailbreak your Samsung phone to allow you to put a custom-built Android kernel on your phone allowing you to use a newer Android OS, but who wants to do that shit? It's a F'ing *phone*, man, not the year 1991 where I'm setting IRQs and DMA channels to get a new peripheral working with >601kb free conventional memory in CONFIG.SYS on my AT-compatible desktop PC for crying out loud. Again, it's a phone. Don't wanna think about it, just use it.
There's a reason that Samsung has gone from the Galaxy 2 to the Galaxy 5 in the time that Apple has gone from iPhone 5 to iPhone 6, after all:
Ever seen that one Warner Bros cartoon starring Bugs and Daffy Duck where they're competing on a vaudeville stage for applause? Bugs comes out and does fifteen taps of a softshoe routine and receives huge applause, then Daffy tries to one up Bugs with a wild dance routine that only get crickets from the audience. Then Daffy looks back out from behind the curtains and *POW!* he gets a rotten tomato dripping off his beak?
Samsung is Daffy Duck. Trying way too hard.