If there is one company I trust to not screw this up it's Google and I think they have a good shot at getting this right. I'm sure their partner companies are going to be a bit ansy to start but they all compete on hardware / price anyhow which this doesn't change. A few points that pop to mind:
A. They already had to compete with Motorola, so they haven't lost or gained a new competitor.
B. They don't pay for Android so Motorola hasn't gotten some new financial edge. Google just has to ensure that all companies still get source releases at the same time. What they do with them is up to them. (aside: I expect we will see MotoBlur disappear with some of its key features rolled into future Android releases)
C. This will allow Google to protect Android much better which is very beneficial to their bottom lines, especially if it keeps patent licensing costs off of their products.
D. Google just has to be sure they don't play favorites but from what I have seen up until now they have been good about that.
E. This may have just brought the competition for who gets to build the next Nexus to an end. (unless the next Nexus is already basically "done" at another partner company)
I think they can get this right... and now hopefully we can get a whole line of nice Motorola hardware with current Android and unlocked boot-loaders, etc. I might have to reconsider the Droid 3 again (more like Droid 4 one day, since 3 is already in the wild as is)