I usually just want to change the kernel to the latest version.
All the other OS versions are of no interest to me. Even if they were, a single drop-down menu may be faster, but it would be easier to first select the major version, and then possibly a different point release than the latest. (The latest point release should always be the default.)
Also: please test your UI changes on laptops with little vertical space. Your new UI (as of 2015-06-15) that replaces the standard pop-up menu? I can see four (4) options on my screen, so finding the latest point release of the version I'm using has just become more annoying.