Hey I bought that Sica! I liked the switch replacement system but I ended up never replacing them, as I only used the mouse for a few months. It's not a horrible mouse, just a bit too narrow shape with a weird side grip angle, and a meh build quality (considering the price and the ROG tag, it's a joke).
Not sure how popular the G100 shape is in practice, but I think it has a lot to do with how it's advertised. As (I think) Derp pointed out, the simple shape and low weight would win a lot of people over if they bothered to try it and disregarded the current marketing gimmicks of "bigger, higher cpi, heavier, shinier, more features" = better.
If Logitech started advertising these as high end gaming mice, instead of low-tier desktop/gaming, I'm sure it would be more popular.
Then again, I'm probably a biased user regarding the shape, as I started computing with the mouse shown below. And even at the time, switching to bigger/ergo mice made no sense at all (not that I didn't try), my dexterity with these was much better:
Edited by Kirisu - 8/4/16 at 9:41am