I did finally figure this out - you use the scroll wheel to zoom in and out. The red target bracket doesn't show until you start scrolling. Hope this helps, Alex.

It's cool by me but I'm using a lame touchpad scroll these days and it's too sensitive for that.

Nope. I can move in and out with the scroll button but I don't get any brackets. Do they do anything?

They don't "do" anything, purely informative. When you zoom with the scroll wheel, it zooms centered on wherever your mouse is pointing (as opposed to using the graphic scroll bar or the keyboard, which zooms centered on the current view). The brackets just appear while it's scrolling to identify where the new center will be once the scrolling's done.

Ok good. Then I can live with not knowing why I'm not seeing them.

It all balances out. A guy on a linguistics blog I read was bitching that Bengali script does not render properly for him in Firefox but it does for me.

So I get Bengali but not Google Maps brackets.