Yeah, that's one of the things I don't like. The size, and especially the location, make that button essentially useless for me. For those of you with this mouse, is it at all possible to actually use it? It seems like you'd have to move your entire hand to hit it.

Again, on my MX1000, it has buttons directly above and below the scrollwheel. I have them remapped for functions other than they were originally intended. The top one is my middle button, Bitt. I used it constantly to open links in new tabs.

I know nobody is interested, but here are the button mappings on my mouse, which I could not use my computer without:

Thumb buttons on the side:
Ctrl+W
Ctrl+Tab
Double click

Buttons above and below the scroll:
Middle mouse button
J

That last one is the only one I could probably live without. It's there purely for my Google Reader obsession All the rest, aside from the double click, of course, are for web surfing.