Hey it's about TIME they gave us getElementsByClassName(). Christ, that waited about a decade too long.
Meh, the fact that you don't have to follow any particular style in HTML5 is precisely because... you really didn't have to with anything else, unless you really really really REALLY were serving REAL XHTML. But you weren't, we weren't, nobody was, everyone wrote whatever and the browsers knew how to just DWIM.
So the HTML5 spec says, since that's the case, fine. Leave it. The only people who would even bother reading new rules about quoted attributes and closing slashes are the only people actually practicing it anyway. Those who never did, never will. One of the goals of HTML5 was to document what browsers actually gave a rat's about.
Though the funny thing abotu quoting your attributes is, it's way lazier and easier to just do it all the time. Your other option is to memorise all the edge cases where it breaks s. everywhere.
If you're not quotin' yer attributes, you must be bored and lookin' for sumthin' to do.