Quite, anything else is a sledgehammer to crack a nut.
Many new mac users reach for special tools to do things MacOSX can already do.
Though of course if you have your photos organised in the MACOSX supplied iPhoto which is the default Application for importing any pictures onto your Mac, then Preview wouldn't be the way you would be viewing your photos.
However a good tip about preview that you made is that it does have the advantage over iPhoto's export in that it actually gives you the size the file will be when exported
