Hi Baby Boomer - I have Mountain Lion 10.8.3
Yesterday when looking at a tutorial I found that Finder should open with the Home icon (the house) but mine was opening with All My Files and the house icon was not showing at all in the pane. Somehow (don't ask me how) I managed to get Finder to show the home icon and my computer name and when I click Show View Options on this then I do indeed get the Use as Default Button. I haven't quite worked out how to send you a screenshot of the window, but if you have Mountain Lion 10.8.3 same as me, if you look at Finder under All My Files you might see no Use as Default button?
This is my first Mac and I've had it less than a week - there have been some funny anomalies. When I first switched on it came up with the utility Voice Over and wanted me to hearn how to use it to Set Up!! I finally found out how to close it (Google on my old PC!) and it seemed quite a few folk were having the same problem. Oddly, although I have bought and paid for "Pages" and it is showing me it wants updating, when I try and update it my Mac tells me I haven't bought it!
Will try and send you a screen shot when I look up how to do it!