I’m one of those irascible lefties.
When I used to do Desktop Duty at work, I’d always put the mouse on the left side, just for fun. New users were very confused.

Waaaaay back, Microsoft had righty AND lefty ergo mice. No more lefties. Most trackballs are set up backwards too (righty).
The absolute WORST is my rack mounted keyboard/flat panel. It has a tiny touchpad on the right instead of a mouse, so it’s doubly uncomfortable to work.

That aside, I just use my mouse on the left side and keep the buttons as they are. It helps when I’m at someone else’s computer.

Of course it’s also a lot of fun to make the buttons left-handed for righties too. Or if you get bored of that, you can rotate the display 90 degrees [cue evil laughter].

Here are some helpful tips before making the switch from a right handed to left handed mouse:

* Learn and convert to using as many keyboard shortcuts as you can before you try switching mice. The more you can do without the mouse the easier on your hands and the easier a transition to a left-handed mouse will be.
* Don’t try to switch to left-handed mousing when you are otherwise extremely busy or stressed with work. You need to be able to allow extra time to do things at first.
* When you are ready to switch, do not take a phased approach. Do not say “I’ll try it for an hour a day.” If you do that it will take 10 years for you to become accustomed to the left handed approach and you will give up long before then. You have to dive right in and use the left hand 100%.
* Relax and don’t beat yourself up when you are slower to accomplish tasks on the computer until you can get up to speed with the left hand.
* Do not configure the mouse as a “left-handed” one, just move it to the left side.