Durability

The Diamondback 3G seems like an even sturdier construction than the old Diamondback. The shell of the mouse is now black and painted with what seems to be a really tough paint. When it comes to buttons the ones on the Diamondback 3G seem to be a bit more firm than the ones on the old version. This is a pleasant surprise and means that the buttons don't pop out as easily as before. The firmer design also helps to prevent that the buttons slide in towards the center and block the scroll wheel’s action. This was a real problem with the old Diamondback, but seems to be fixed in the new version.

The mouse feet are really soft and not that tall which means that you will have to replace them not long after you bought the mouse if you use a mat with a rough hard surface. Normally this isn't all that big of a problem because most Teflon companies provide you with precut thick quality Teflon, but this isn't the case with the Diamondback 3G. This leaves you with two options either apply some thick precut Teflon originally shaped for either Logitech or Microsoft mice and then deal with the buildup of dirt under them or buy some Teflon tape and then shape that up. The problem with using Teflon tape (besides getting it to stick) is that it's hard getting hold of the quality kind.

Comfort

Razer's Diamondback 3G is quite comfortable to use even over an extended period of time. The design of the shell has bents and curves at the right spot enabling almost everybody to grip it in a comfortable manner. Its only real problem besides being so thin is the fact that the side buttons are placed too far to the back of the mouse making it hard for people with large hands to use them.
Overall the ergonomics of this mouse is better than average, but far from being the most comfortable fit out there.