I will be dead honest here and just start with this. For $30, I really didn't expect much at the start, and I am really surprised I like this mouse as much as I do. There are two small issues I need to address, though. The first is something I don't see a lot, but while writing, I tend to have the music up, quite loudly at times. This is also a test for me to see where the sensor stands when acted upon by outside vibrations. While at 500, 1000 and 1500 DPI, I saw no deviation of the pointer with the music turned way up. Once I set the X-G510 to 2000 DPI, the mouse pointer did dance pretty freely on the screen at that point. While there is little to be done about it, this is something I don't tend to see in laser mice.
The second thing is the finger-side button on the right side of the mouse. While the button on the left is easily worked with my thumb to press it, the button on the other side leaves you always contorting your hand to access it. While it is great for the left hander's out there, even they will have issues when trying to use the left side button.
What I do like is that the Avago optical sensor tracks really well, and even trying to move the mouse as fast as humanly possible to try to make the mouse fault in some way, I was unable to get it not to track with the pads I tested it on. I did find myself using the 2000 DPI most of the time for my testing, as the shape of this mouse lends to having your hand rest on the table. Speaking of DPI, I really liked the blinking light under the button to easily show me which of the four DPI settings I was on by the speed of the flashing LED. While we are on the subject of LEDs, the bright blue one under the lightning adds a crackled look to the top of the mouse, and since it goes so far forward on the mouse, it's like your fingers are shooting sparks, because you can see the ends of the pattern on the sides of your fingers. On top of an aesthetically pleasing and pretty universally comfortable fit for any hand, and having the straight forward software Genius provides is just icing on the cake, in my opinion.
What it all boils down to is this. Genius made a mouse that anyone and I mean anyone could easily get used to. Even being based on an optical sensor, the 2000 DPI and speed adjustments in the software will take this mouse into the comfort zone for any user's idea of perfection. The X-G510 comes with everything you need, right out of the box, and after a fair bit of use, I really can't complain too much at all about this mouse. Once you factor in the fact that when these become widely available, the MSRP of $30 will make this a great option for an individual purchase, a gift to your favorite lefty out there, or even just as a really well done extra mouse to travel with your laptop.