I'm not following the first part of your question Bonnie - please elaborate.

As for learning curves, obviously you would have to learn which programs you want for what but I think KDE itself is reasonably similar to Windows like XP, etc. My parents who are in their 70s had no problems changing from Windows 2000 to OpenSuse. They actually found they preferred it as better reliability meant reduced the occasions they had to call me for help considerably. That said, I do install it for them.

Hardware wise, Linux continues to improve but I think it is advisable to do a bit of research to ensure a device is compatible before buying a new device. As for existing devices, you should be able to test some things with a live CD/DVD.

Some things need additional steps (eg. I have to follow these instructions for our laser printer, our Epson scanner needed a driver from the Epson download site) but a fair amount (including our Epson P50 printer, HDHomeRun TV tuner, Yamaha mixer, Zoom H4 recorder, UM-2 midi interface, etc.) "just work". I was even able to find something called Plug to work with my Fender Mustang amp!