Yep, G5 seems to the best way to go now days, affordable and great for gaming.
The reason people buy new mice is that they have more comfortable design (some of them anyway), added buttons, for example the G5 mouse has 2 side buttons which help me in other games, it also has a tilting left and right scroll wheel which isn't really that important but you can use those tilts as functions in games if set up right.
The grip of the mouse is nice, it also has 3 different speed settings on the mouse, a slow, normal and fast speed setting, usually you use normal for general computer usage and fast for gaming if you really want to without changing in game mouse sensitivity.
And most importantly is how many DPI the mouse can move at.
Cheaper mice have a low DPI, which means that in games like CS, youre aiming is less precise, and if you moved your mouse reeeeeally really slowly, you'll notice that it moves along a kindof grid, it doesn't move super super smoothly, even if you think it does, it doesn't.
You would most notice this in games that require some sortof distance shooting where every little inch of movement counts.
Overall you'll just find that a mouse like the G5 is much better than a crappy $10 mouse and you'll enjoy using it more due to the added functionality, the comfortable design (i'm a right hander but play pretty much all games except RTS games with my left hand on the mouse and it's still comfortable even though the mouse is a right handed mouse), and the larger DPI creating smoother mouse movement in general.
I also almost forgot to mention that the G5 has weights that you can customize your mouse with.
It has a little weight tray and a little container with a set of different weights in it so if you want a light mouse, you dont have to put weights in, but if you want a heavier mouse, you fill the mouse with the heaviest weights and you'll get what you're after.
