I'm running City of the Spider Queen in 3.5: VERY rules heavy. My players can't keep up with the maneuvers and spells they have, and yet they continue to ask to add in more options from the splats.
I'm in the "3E is not rules heavy" camp because its core is a fairly simple mechanic at work.
I find 1st and 2nd edition to be much more rule heavy, because so many of the rules are conditional. There's no central mechanic, so instead you have to either memorize all these "one-off" rules or have your books tabbed. That to me is rules heavy - a complex central mechanic + conditional rules that don't fit the central mechanic.
Its only when you go beyond the core of 3E that things start to get bloated.