I went from a normal mouse to the Logitech MX518 to the Razer Death Adder then finally to the Logitech G500 in that order.
The MX518 was one of the most comfortable mouse i ever used until it broke.
The Death Adder was a disaster i should never have bought. Sweat builds up on the plastic really easily. I didn't like the touch of it because of the hard plastic at the sides. The shiny plastic reminds me of some cheap quality build. The wheel can easily get dirty as well. My hand was aching a lot after using the Death Adder bottom line i hated it.
Then i went for a G500 which is basically an updated model of the MX518. MX518 was replaced by the G5 which in return was replaced by the G500.
The G500 has the same mold as the MX518 but updated as it has a neat wheel feature, the sides were texture which was nice to touch and have a good grip on the mouse compared to the Death Adder which was slick and shiny.
It's easy to adjust the DPI speed using the buttons on the mouse which was good. The scroller wheel can be toggled between 2 different modes. a Stiff wheel and a free rolling wheel. I use both for different situations :}
People complained that the middle button is a bit of a pain to click, and i sort of agree. But then again i never really bother middle clicking anyway.
Other complaints by others was regarding the side keys which was a bit of a sore because you can accidentally press another unintended key if you aren't careful. Yeah it does sort of feel like that, but then again i don't use the side keys at all.
So what matter to me was the nice scroller, dpi switch, weights, aesthetically pleasing mouse, comfortable to hold, nice texturing.
It's not perfect but it works for me :}
PS: The logitech Setpoint software is MUCH MUCH better than the Razer i used for the Death Adder. I have full control for configuring the mouse. I'm still tweaking it gradually to find the g spot, but atm i quite satisfied. I do use the light weights :} People complain about the weight but i am pretty ok with it. Even without any weights it feels light enough for me.