That to me is the most significant of all the announcements listed.
Additionally, it only says that the devices will receive the latest upgrades for 18 months after the device is first released, which is problematic in many regards. If you get a phone the day it releases and are forced into a two year contract (which you almost certainly will be if you are going with a carrier), then for the final six months, or 25%, of that contract period, the carrier is not required to allow for you to receive Android upgrades. That instantly devalues your device. And what if you get a new device, but not until six months after its release? Well, then your carrier is only required to permit the upgrades for the first year; the last year is back to same old, same old.
And it says nothing about how timely the upgrades are. As it currently reads, all it guarantees is that for a year and a half after the device is released, carriers must eventually allow your device to upgrade to the latest version of Android. It is not a long enough time to cover an entire contract period and it has a little clause that is open to interpretation by all parties involved.
Edit: I'm writing this from the perspective of an American consumer. I do not know anything about the way that carriers and their mobile contracts work elsewhere.
I don't see any reason why the likes of Samsung, Motorola, HTC would go through the trouble of releasing an update just for a couple of customers, ignoring the rest.
So its probably set up as 3 Major version updates as Google/OHA members want that kept at every 6 months..hence the 18 month time limit..
At least Google is listening and doing something about it, though.
Google still has a long way to go if this is all they've got to announce.
Google does need to work on updating, but I find it very hard to believe it slows down Android adoption at all.
BUT many people ignore the fact that the lifespan of a phone is two years. For those of us used to rapid iteration that seems an eternity, but in reality it isn't a bad situation. Compare it - for example - to the time IE6 (and now IE7) needs to be supported for.