I recently picked up a new mouse the Logitech MX Revolution - $99 at Best Buy and around $88 online, which is what I paid using a coupon at best buy. It is one of the best I've every used after installing an add on to the standard SetPoint software. For some reason Logitech thinks you don't need complete control over all the buttons, only the ones they think are useful. Thankfully someone took the time and effort to correct this idiocy from Logitech and wrote an add-in for their Setpoint software. This add-on (available at http://www.mstarmetro.net/~rlowens/uberOptions) allows you to complete customize all 13 control points). Supposedly the built in and non-user replaceable (bad Logitech BAD!) lasts for 13 days, but I have yet to go past 3 days. I can live with that for the moment. Maybe when I send it in after the first year of the 3 year warranty they will send back one with a replaceable battery.
After getting the MX I had an itch to replace my aging keyboard as well. I switched to the Microsoft Natural Pro keyboard about 7 years ago, maybe longer I don't remember. Once I got used to the split style keyboard I couldn't go back. My wrists stop hurting and I could type much faster. Anyway the one I was using was getting old and I had to tear it apart every 6 months or so to get it back to working order. The left shift key was particularly a problem... I had purchased a backup several years ago but it was unfortunately dropped and had problems of it's own.
Replacing Natural Pro with the Natural 4000. I was hesitant to change but I ran down to my local OfficeMax and thought if it sucked I could return it, I didn't but it's good to have the option. In fact OfficeMax matched the price I was getting on Amazon so I saved $10. The Natural 4000 is a great keyboard. No problem changing over from the Natural Pro except for the change in wrist position thanks to the front riser. Don't get rid of the riser if you can help it. You wrists will naturally fall into place if you are desk top typer like me. It is almost silent and the key action is very smooth. Plus I can replace it if needed within an hour or a day at the most. Something the Natural Pro could no longer provide.
If you spend a lot of time at the computer invest a little and get a Logitech MX and the new Microsoft Natural 4000. Customize the software programmable buttons for both and start getting things done a little faster and with less stress.