After at least six years of use, my mx518 is wearing out.

It still works flawlessly for me, but the scroll wheel is starting to jam up.
The mere fact that this thing has lasted so long under such heavy use is all the endorsement I need to get another one. Unfortunately for me, they stopped making them. Probably fearing customer revolt, they did replace it with a nearly identical model, the G400. It's cheap so I ordered one.
Has anyone used the G400? I have one of the good old mx518s with the five small glider pads and I'm worried that it won't be able to live up to the standard set by the venerable mx518