While the extra buttons are a little stiff for fingers that normally don't have to click, and the positioning is slightly off (or my hand is too small-) the mouse is great. Very sensitive.
The software could be better. The default maps all the buttons to functions within the software, so if you don't UNmap them right off, you will suffer your game minimising and potentially crashing as it switches from your game to the EREBOS software activated by you clicking a button that's pre-mapped.
This is further frustrated by the fact that each profile is set up with these defaults so if you don't UNmap the profile switching button it will be switching profiles on you while you're wondering why your game minimised. Tabbing back to your game will then leave you with a new profile for the mouse and instantly switch back to the software the next time you click one of the extra buttons.
Once you've worked that out… It becomes a better experience to just clear every profile and then set up each button in each profile as you need it.
Sadly most games don't cater to all the extra buttons. But EREBOS software does allow you to map the mouse buttons to keyboard keys, allowing you to map, in the game, keyboard keys that you won't use, and then map the mouse buttons to those keys.
Slightly convoluted, but it works.