I've had the X8 for a couple of months now, and while I'm very happy with it, there are some features I miss.
- The wired/wireless system is awesome: forget about batteries or charging docks.
- The 3 different speed buttons are very useful when playing, specially on shooters.
- I like a lot how the buttons feel: It's almost impossible to hit a button accidentally.
- Very good response time even for a wireless mouse.
- The macro button is useless, specially since there are only 5 programmable buttons and you'll probably have most of them already assigned.
- The shortcut button to the games folder is rather useless, it's a lost button.
- The lights are not as cool as they're on the picture: The red lights only glow while charging and the blu light of the bottom isn't actually visible when the mouse is on the table.
- Probably not the best one in terms of ergonomy.
I'd say it's totally worth if your needs are like mine: need a wireless mouse (I can use it from the bed :-P) and also want a good device for gaming. If you don't need the wireless, look some other mouse, it probably will be better and/or cheaper.