Most apps have Linux equivalents. e.g. -- OpenOffice for Word. GIMP for Photoshop. Firefox for IE.
For those who don't find close good enough except in horseshoes, there are ways to run things. CrossOver is a proprietary app for which you must pay and which will run some Windows apps on Linux.
WINE has been a very long-term project. I read not long ago that Google paid some programmers to add some functions to WINE to let it run a few popular Windows apps most likely to be needed in Linux.
We tend to think the world stops at the US borders. Linux is apparently growing much faster outside the US.
In Mexico City, a few years ago, I installed Mandriva dual-boot on a computer in a government office where my nephew was computer guru.
This year, the office where he works now is going to completely defenestrate Windows and install Mandriva. Most people in Mexico pirate Windows for about $5 USD, near a certain street downtown. But as a political party office, they cannot afford to be caught pirating, for political reasons, and don't have the money to buy Windows and its apps, nor to buy all new computers so they can use Windows. I forget how many computers, but it was hundreds at least.
I asked if they had any special apps, and he said, yes, but they were written for Linux.
I do not know if my presenting Mandriva had anything to do with this decision to use Mandriva or not.
Employees have been told there is no point in avoiding Linux, and most have no problems clicking on an icon in Linux for the same function they use in Windows. Training time on an installed and working system is a red herring. I taught a women friend in rural Mexico to use a Linux connection to hotmail in maybe two minutes.
My daughter-in-law in Virginia learned to use Puppy live on her busted Win 98 computer for her e-mail in no more than ten minutes.