The thing about the new numbering system is that older versions, like 3.x, get left behind quicker and perhaps support dropped sooner? I'd imagine they were tired of people hanging on to the last major release so want to make that line between versions harder to recognize and hopefully get more to update sooner. It has plus points and negative.

System Administrators, Website designers and Addon authors have to move faster to stay compatible and keep up with the constant changes, changes which are harder to identify.

With the old version number system, it was easy to tell when a major new release needed close attention and testing of addons, software and hardware compatibility (v4 onwards requires SSE2, Athlon XP goodbye or stick with v3). Now it's harder to know when a major release is a major release, or a minor update like v4 to v5.

Yes a number is just a number, but the old system just made more sense to me and was more useful to give users a heads up on major changes.