[WiseWeasel]

I'd rather these complex sites avoid having drop-down menus entirely for their top-nav bar. Instead, have the most common general sections linked in the top-nav, and put links to their sub-sections in a section-specific navigation area inside the newly-loaded general section, separate from the top-nav. Less common pages and sections are linked in the bottom-nav.

Cluttered top-nav is a hassle to use, with the worst offenders making me feel like I'm looking for a needle in a haystack every time I use it. It's much nicer to drill down to the section you need one step at a time without modal navigation windows appearing and disappearing, especially if the defaults are well-chosen.

[It's also worth noting, as mentioned by others here, that the paradigm of stacked windows, and thus pull-down menus, is incompatible with pocket OS designs, so you're going to end up with completely different navigation workflows on different platforms if you go this route.]