Hi Earl, There are a couple of things that you can do that make the Mac look like windows from a keyboard standpoint. One of them isusually done and that is to be certain that full keyboard access is selected under keyboard shortcuts in keyboard and mouse. The other is to make sure that tab highlights links on a web page is checked in safari's advanced prefs. Menus are consistent and once you have learned one menu structure, most are the same. most apps have a preffs dialogue which you access for instance using command-comma. There is also a lot of good help available on various web sites.
I would say that the learning curve for the Mac is not as steep as that for windows and a screen reader. The Mac comes with some good orientation fascilities such as voiceover help, keyboard help and a nice interactive getting started tutorial.
