Why Android Updates Are So Slow
Some notable points:
The manufacturers' third-party UIs ("skins") get blamed more than anything for upgrade slowness, and it's easy to see why. After all, they are visually prominent, and seem to be the only tangible difference from a Google Nexus phone, which typically launches with the latest Android version. But most of the work is actually fitting Google's new software to the hardware componets. "It's not as simple as, if we didn't do customization, just downloading a ROM from Google. That wouldn't work," says HTC's Drew Bamford. "So, even if we did no customization, I'm not sure that the process would be much faster, to be honest."
"I can tell you that when we release a new product to carriers, we can have it running in our labs for six months before it's released by the carrier," says HTC's Bamford. "It can take a long time." T-Mobile's Young confirmed that it is typically three to six months from the time they get the new software until it goes live.
How did Apple manage to skip that exhaustive carrier-testing that everyone else had to go through? It didn't. It had to jump through the same hoops as the Android manufacturers; the only difference is that Apple jumped through them before it announced the update. Sprint's Ryan Sullivan explains: "I don't think that Apple is necessarily any faster, I think it just appears faster because when they're announcing the OS release, they're launching it.
I also think some of the blame lies on Google. Since they develop Android secretly for Nexus devices and then release source, they are forcing manufacturers to ship old versions of Android.
Also, you cannot compare commercial manufacturers with hobbyist developers. There is no guarantee that a custom ROM will be stable on your device and make optimal use of hardware, while companies like Samsung or T-Mobile will experience significant negative press if an update is buggy.
The article does get one thing wrong:
Nexus devices are first in line; Google works closely with its chosen hardware manufacturer to go with the new version of Android, and then it works with the wireless carriers to make sure everything is tested and ready to go ahead of the announcement. That only works at launch, though; older Nexus devices will still have to go through carrier certifications just like everything else when a new OS update comes in.
This is only valid for previous-generation carrier-locked Nexus device, not anything sold unlocked or from the Play Store.