yes Marius, stay away from the 10 Quid set :)
The G5/7 are definitely gamer favourites. I had one not too long ago, and recently donated it to someone when I got my notebook mouse.
Dont get me wrongo, they are nice mice but I must admit, the whole weight adjustments thing is a bit wanky.. are peoples hands really that sensitive??
There are many small muscles that control the hand in grip posture. They work in small twitches, as opposed to prolonged load bearing contraction(like muscles in the hips and lower limbs)
A few grams here or there isnt going to affect the way these hand muscles are working, it is moreso the overall body and shoulder>elbow>hand posture of the 1337 g4M3R wanting to sway the outcome of 84 straight constipation ridden hours of Starfcraft/WOW
So yes, the G5/7 are nice, but I wouldnt invest too much in the adjustable weight business.
If you like things a bit weird or futuristic lookin', check out the foldable arc mouse (
http://www.microsoft.com/hardware/mouseandkeyboard/productdetails.aspx?pid=112) ;) Also from MS, but not BlueTrack IIRC
mtfbwya