I suffer from RSI and need a wireless keyboard with an easy and smooth action. I enjoy the shallow action and flatness of my Acer laptop keyboard but the only thing I have found for desktops is the Logitech diNovo Edge, which is very expensive. Also, Tom's Hardware has a review of mechanical keyboards, all using Cherry MX switches, and I wonder if these would be better?
if you want to match the style of keyboard found on laptops then you need scissor membrane switches and not rubber dome switches found on most low end cheap keyboards.
the addesso compagno 3 is around $80, the dinovo edge is around $90. i've had good luck with logitech products in the past myself so you should be able to get several years out of it.
lets say it lasts you two years, that is $45 per year. as long as you do not destroy keyboards and take care of it it would be a good investment. if you destroy keyboards you could just buy $10 rubber dome switch models but then you will suffer as they are horrible to use day to day.
remember: mice and keyboards are your only input devices and are very important. people often do not consider them very important so often try to make due with cheap solutions which do not work well. it is better to spend the money and buy something comfortable for you to use. after all, do you buy uncomfortable chairs? clothes which do not fit?
as far as mechanical keyboards are concerned?
far superior to rubber dome switches. keep in mind that you will spend at least $80 on a cheap board or over $100 for something in a main brand flavor.