Having used a regular mouse for decades, pain in my hand, forearm and shoulder necessitated a change. I saw this brand for sale new and it was above my budget, especially when I didn't know if I'd like it or not.
I find that it is very comfortable, but of course it does take getting used to.
Using software, which is available on the manufacturer's website, some button functions can be customized.
Not disappointed! I highly recommend the product.