I don't really like it myself, I think it should be an option along the lines of simple finder.
One problem I have with it is it's not always visible. That combined with the fact that it's ordered by last used causes some slow down. Instead of being able to immediately see (in the dock) that I need to go three to the right. Couple quick clicks and I'm there.
With the Panther version (assuming its not the app you were just using) you need to hit cmd-tab then wait a moment for the bar to pop up, then take a look and see if you've used 4 applications (that are still launched) or 5 applications since you last used the app you want.
The other problem I have is that it's mouse sensitive. So if you're jumping between a couple apps cutting/pasting or just needing to reference one then go click on something in the other you need to switch applications THEN drag your cursor across the screen. In jaguar you could cycle through your apps as you positioned the cursor for the button or text box or whatever.
~BS