I have a Natural 4000 and love it.

It all depends if you have suffered from RSI. I used to type on a normal laptop keyboard all the time. Then I got pains along the top of my forearms, i.e. RSI. I switched to an 4000 and I haven't had that pain since.

The most important thing to do is be aware of your body. If you get stiff or sore or pains or certain joints/muscles feel tired, that's your body trying to tell you that you are doing something wrong. Listen to your body, adjust how you do things.