A great mouse, I've had it for about a month.
The mouse works 8 hours a day every day and I haven't changed the batteries yet.
It fits my hand perfectly.

The scrolling became almost useless after a year of use, it jumps up and down on the page when you scroll down.
Also, the curve it forms at the base didn't suit me compared to other ergonomic mice.

I bought it because of tennis elbow. I found it helpful from the first day. I would like it to be a little heavier in the hand. The only drawback for me is that the scroll is a bit higher and not as ergonomically comfortable. However, it is worth its money.

Watermelon is rubbish.

After 2 weeks of use, my arm started to hurt a lot and I would wake up with incredible headaches at the back and above the ear, all the way to the shoulder blade.
I thought I was sleeping wrong, that it was the pillow, the mattress, or even Mercury being retrograde...

The pains would start on Tuesday morning and stop on Saturday.

I realized that it was the mouse's fault, so I got another simple one to test and the pains stopped after 2 days.

It's not worth it in any case, especially for the price of 40+ euros (I got it on sale for 25)

I bought it after the cheapest, ergonomic Gembird, thinking that from the appearance it would be of better quality and better grip. Oh no! It is very strange and difficult to use, at least in my hand (an average woman's hand). Maybe it is more convenient for small hands. Especially for large hands, I would say don't even try it! The Gembird is much more user-friendly and fits better in the palm.