Love my Atrix HD... but not sure how this is news...
I would still go with the Atrix HD over the Samsung Galaxy SIII even if both were the same price.
The UI on the Atrix (and Motorola in general) is the most pure version of the Android without being a Nexus phone. The construction, the bright screen, the non-fingerprint-magnet body, the speaker and audio quality makes it my choice... the camera is crappy... but its a camera-phone camera... oh well.
Unlooked bootloader? You can do this on almost every phone out there....but of course it would void the warranty. Still, wouldn't buy it though because the Nexus 4 will be the best phone on the planet when it comes out next week. I'm so gitty right now....can't wait for my Nexus 4. If it wasn't for the Nexus series, I don't think I would own an Android phone. Once you've experience a pure Google device, you'll never want to switch back to a carrier/manufacture branded one.
I don't know why all Motorola phones are not Nexus branded phones since Google owns them.