Excellent article Cheryl. But I've already gone down a different path with frames for navigation.
I have several personal sites (not commercial), with 1 very large site (5k pages and 10k images) and several far smaller ones. Purpose is to provide broad and deep information, so there are a lot of pages. Been building all these since 1999 and have great stats for a personal site. They are all based on frames for navigation and organization. The topmost page has navigation button links to the major sections - so no matter where you are in the site there is always nav. Everything was originally done in FrontPage, although I never used it's navigation functions (too limiting, yes). Everything is now Expression of course.
The big site (http://www.drivingenthusiast.net/) is just too darn massive to change unless I know for sure that I've some up with a superior design, and one that still allows me to add pages easily and quickly.
The smaller sites (such as http://www.s2000enthusiast.com/) can be changed and could perhaps be used to experiment a bit on a better design. I looked at SiteNav and may use it. I may also switch to a dynamic template or master page scheme as well. And yes, I know I need a serious CSS plan - but it's going to be murder to implement it in the big site because of the sheer size of the job it would take to go back into every single page.
The problem with SiteNav or any link bar with drop-down menus is that I feel my big site is too large for this type of design. I have held the major subject areas (along the top frame) in the big site to 9 areas. Each of those areas links to a page that builds the frame for that section and has a navagation menu to the right for 10-20 "sub" topics. So if I used SiteNav here, I'd have to build the 90-180 new frame pages necessary for all the new links. That's a heckuva lot of work to provide (and maintain) direct navigation, versus forcing people to go down my hierarchy. That's why I never did the major navigation with FrontPage's (crude) tools in the first place.
Note that for my left-hand navigation within a subject area I did once implement a third-party DHTML/javascript drop-down menu to attempt to categorize the "sub-topics", but the code was slow and performance was poor. I've since removed it and am looking for something better - particularly to use on the main page where I have an atrocious number of blog categories to organize.
So lets say I started over from scratch on one of my smaller sites with the goal of coming up with a perfect design and rolling it into all other sites. Why should I use something like SiteNav or some other menu bar and skip the "hierarchical" frames approach? Some sort of a template or master page with CSS is a given, but navigation has me stumped for a better way.
-Jeff