Deetee 

Thanks. Is it easy to navigate with a trackball between 2 or 3 screens, and kind of fast as well?

Yes. You can vary the sensitivity and accelleration. When you spin the ball fast it can move very long distances quickly or move the ball slowly for precise positioning.

So, some months ago I ordered 6 different 'alternative' mouses, like Evoluent C, Evoluent 4, Handshoe mouse and Penquin. All 30 days on trial.

I especially liked the Evoluent because of several programmable buttons, but my wrist started to hurt also with these ones.
Also the handshoe mouse at first felt as a really good support, but also pain here.
The penquin seemed to be OK for my wrist, but decided to look further.

Then I found Penclic. It's a pen and mouse combined. The reviews were mixed, but I gave it a try. I ordered the D3 as my logic says the wireless version can only be slower. I have been working with it for about 2 months now, and I can say this one works much, much better than the Wacom pen tablets that I have been using for the last 10 years. It's faster and easier to operate. For me it's a big improvement.

Just wanted to update this thread with this experience

Thanks all for contributing