I give it 4 stars for the following reason: the battery life and charge.
I come from an Xbox Elite 2 Core, and I admit that the Revolution X outperforms it in competitive PS/TPS games that want to optimise every millisecond, adjust sensitivity, reduce dead zones, etc.
The addition of the S1 and S2 buttons is perfect, although it takes a little while to get used to them.
Great customisation: both hardware (stacks, crossbars, weights, triggers) and software/profile from the screen itself. If you like to adjust every detail, this controller allows you to do so quite well.
Although I've only had it for two weeks, I have to admit that coming from a controller with rear sticks, it didn't take me long to get used to the rear buttons.
In short: the Nacon Revolution X Unlimited is a very competent controller with lots of features, designed for demanding gamers. If you take advantage of what it offers — Hall sticks, configurable profiles, extra buttons, etc. — it's one of the best options on the ‘pro’ market for Xbox/PC.