Nice pictures(from overclock.net I believe)! Wished logitech started to use a metal Construction in the base (bottom of the mouse. Logitech has shown no interest in producing mouses with partly metal construction before so I find it unlikely that they will do it.
Metal adds weight .
Yes it does. Other companies (crosair,mad catz) has done this without a problem IMO.
I wouldn't say it's without problem; the weight it adds is significant and I would imagine it also adds to the cost compared to plastic. Most of the mice that use metal are also mice that sell themselves on gimmicks, Logitech products, while they are not without gimmicks, they usually just rely on being solid and well designed to do well rather than gimmicks. And it seems to be working.
That said, I am a big fan of things made out of metal, so I would love to see more mice using more metal. So far, though, metal hasn't really been a good thing. The features on two mice I have that use metal, Level10M and RAT7, all seem to just be there to tick a box on a checklist. The Level10M has side buttons because mice need to have those, but they are awful in use. The RAT7 works ok, but they're nothing special. Both are mice that have had more than average work put into the visuals of them, but very little attention has been paid to function.
I'd much rather have Logitech's way of doing things, the button design on the G700s, G600 and G602 is very intuitive and much better than on most mice I've tried.