G5 is my mouse, it is much better than my previous mouse the mx700. The feet on the mouse is the final blow to all users who says the mx518 is better than the G5, since it lacks a second thumb button. The gaming feet on the G5 are huge and slick. If you look at your 510/518 you will see you have tiny, shitty gaming feet. The G5 is a completely new feel when you move it, it will glide over sandpaper >.>... for about five minutes 😀.
The G5 also has the adjustable weights, wich can be a whole lot better than changing sensitivities. The weights are definately a nice feature, I'm guessing alot of people don't think so. The only problem with the G5 is the middle mouse button is a bit difficult to press at first, you might accidentally apply pressure the wrong way and you hit the left/right scroll.
As far as mousepads go, the expensive ones are superbly overrated. A plastic/cloth mat cannot be improved but so much to be worth 50$. And since the icemat feels a hell of a lot like my xtrac hammer, I took the stupid thing back.
Turn your sensitivity down, get a large mousepad, buy a gamepad and ditch your keyboard. This will make you play better, there is no way it can't improve your accuracy and speed of accuracy. By allowing you to turn down your sensitivity you can be more precise. Having a big mousepad means you wont need to pickup and move your mouse or run out of desk space. Getting a gamepad means you dont need to twist or have your keybaord hanging off of your desk, or putting it in your lap..
Your keyboard/mouse setup is just as important as the speed and power of your computer. There is no use having a good mouse if your computer can't run the game. The same thing goes if you have an Alienware and a Packard Bell ball mouse.