I'll second the Kensington Expert Mouse suggestion. I've also been using them for almost 10 years - with a two or three year break right before the current optical one came out. (I had gotten sick of constantly having to clean the older ones, and switched to optical Logitech trackballs for awhile.)
I could not really recommend the older models, but the new optical one is great. Very comfortable, easy to control, excellent button response, and no cleaning problems.
And if you're a Windows user, the Mouseworks software that Kensington provides is excellent. The Expert Mouse has four fully programable buttons, plus chords for the top two and the bottom two buttons (essentially 6 buttons.) Ctrl, Shift, and Alt combinations (any combination of 0-3 of those keys plus any of the 6 buttons) are all fully programmable and can be mapped to keyboard emulation, application menus, custom pop-up menus, etc. It's insane. Way more functions then I will ever need to use - but what I do use saves me a significant amount of time every day.
I would assume that the Mac version of Mouseworks is similar, though I probably shouldn't make assumptions about those crazy single-button mouse people and the software they use.
OK, that last comment may invalidate everything else I said - but I'm sounding like a damned advertisement anyway.
Back to the original question about ergonomics: The most I can really say is that I find the Expert Mouse comfortable, and I've never had problems in my right (mouse) arm. I can't say that I know it would help with wrist pain, but if you decide to go with a large trackball I would definately recommend checking out this one.
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I'll second the Kensington Expert Mouse suggestion. I've also been using them for almost 10 years - with a two or three year break right before the current optical one came out. (I had gotten sick of constantly having to clean the older ones, and switched to optical Logitech trackballs for awhile.)
I could not really recommend the older models, but the new optical one is great. Very comfortable, easy to control, excellent button response, and no cleaning problems.
And if you're a Windows user, the Mouseworks software that Kensington provides is excellent. The Expert Mouse has four fully programable buttons, plus chords for the top two and the bottom two buttons (essentially 6 buttons.) Ctrl, Shift, and Alt combinations (any combination of 0-3 of those keys plus any of the 6 buttons) are all fully programmable and can be mapped to keyboard emulation, application menus, custom pop-up menus, etc. It's insane. Way more functions then I will ever need to use - but what I do use saves me a significant amount of time every day.
I would assume that the Mac version of Mouseworks is similar, though I probably shouldn't make assumptions about those crazy single-button mouse people and the software they use.
OK, that last comment may invalidate everything else I said - but I'm sounding like a damned advertisement anyway.
Back to the original question about ergonomics: The most I can really say is that I find the Expert Mouse comfortable, and I've never had problems in my right (mouse) arm. I can't say that I know it would help with wrist pain, but if you decide to go with a large trackball I would definately recommend checking out this one.