Another vote for Uberconference. Call quality is consistently good, it's nice to get the visuals of callers along with the LinkedIn data (though that's only right maybe half the time) and the controls are easy to use.

Screen sharing is very slick as well, so long as the sharer is using Chrome. The only thing I find missing is the ability to share mouse/keyboard control, but in typical conference settings that's usually not a frequently used feature.