1. It has 3 onboard presets, 2 of which default to numpad keys I believe.
2. Yes.
3. It felt significantly wider than the Naga, especially because of the G-shift button.
4. All mice get dirty with use.
Better wait for a V2 or something however. At its current state it suffers from tracking issues and no flashable firmware to fix them with:
http://forums.logitech.com/t5/G-series-Gaming-Mice/G600-Mouse-Movement-issues/td-p/863548
http://forums.logitech.com/t5/G-series-Gaming-Mice/G600-Mouse-Pointer-Delay/td-p/904278
2. Yes.
3. It felt significantly wider than the Naga, especially because of the G-shift button.
4. All mice get dirty with use.
Better wait for a V2 or something however. At its current state it suffers from tracking issues and no flashable firmware to fix them with:
http://forums.logitech.com/t5/G-series-Gaming-Mice/G600-Mouse-Movement-issues/td-p/863548
http://forums.logitech.com/t5/G-series-Gaming-Mice/G600-Mouse-Pointer-Delay/td-p/904278