I approve. I ride I-77 through Charlotte North Carolina more than I wish I had to, and always alone, whether on two wheels or on four. On the bike, I can take the HOV lane, which spans only part of the urban area, and I always feel safer in that lane than I do in the main scrum.
Inside Toronto, I similarly use lanes for bus/taxi/motorcycle, and again feel a tad safer than outside them.
I think this issue started in the 1980s when a fellow in Washington DC accumulated several pounds of tickets for using an HOV lane on his motorcycle. Eventually, he prevailed and now motorcyclists can use HOV lanes in the DC area. I cannot say whether this permission spans the USA.