The problem I see here is that based on
http://wiki.jqueryui.com/Buttons, specifically example A2 under Visual Design, jQuery UI should have "out of the box" support for a button with only a right icon. The specification that you are proposing, doesn't match what a person is left to expect after viewing the wiki. Furthermore, after viewing the effects of using the "primary" and "secondary" classes, its actually only sensible to expect a person to associate that with "left" and "right" respectively.
Lastly, with Themeroller being pushed so heavily, a lot of jQuery UI users come in contact with the "Switch Theme" button and its only logical to expect that jQuery UI have some built in ability to produce a similar button without having to tweak css as you propose in your post here:
http://forum.jquery.com/topic/a-button-with-an-icon-just-on-the-right#14737000000953129If that were the proper and agreed way to do things then it should be well documented in jQuery UI's official documentation since the A2 button is included in the wiki. Personally, I feel that requiring extra css tweaking is a rather cruel and unnecessary requirement for something so simple and actually common (dropdown buttons). I also feel it does much to work against making jQuery UI "user friendly".
If not you, then who else do I need to take this up with?