The only reason why I think twice with the MX518 is it's getting old. Maybe there are new models that has same reliability but with improved features.
Doesn't mean much, i have a Razer Deathadder(3500dpi) as well and the MX-518(1st version 1600dpi) is just as good and has more progammable buttons.
The one you've linked is the mk2 version and has improved dpi(1800) and better teflon feet.
Another new version of the MX-518 has been released and renamed the G400.
Higher dpi(which you'll probably never need or use)and different cosmetics.Retains exact same shape and buttons.
So it's a solid mouse considering they've been making it for 10+ years in one form or another.