I am right handed in every thing I do…except using the computer mouse.
I have never seen anyone else using the mouse with their left hand unless they were left handed.
Using the mouse with my right hand is awkward, and if I am at another computer, I will move the mouse to the left of the keyboard.
FWIW, I do not change the buttons.
Sometimes, depending on the task and the desk set up.
Sometimes, for no particular reason other than to exercise the left hand.
And to complicate matters, a large number (maybe half) of us lefties use the mouse with their right hands. FTR, though, I have seen righties use their left hand for the mouse at work - usually people who are trying to minimize the effects of carpal tunnel.
Only if I’m surfing porn.
I use both hands for driving a mouse.
I’ve never quite got that hang of these new-fangly dohickey thing-a-ma-gigs.
I’m still getting used to the word “mouse” being a verb.
I’m right handed, but use my left hand for the mouse. When I use a clothes iron, I also use my left hand.
I started using the mouse left-handed after I injured my right elbow. It helped it heal much faster. Once I got into the habit, it seemed more efficient.
Since then, I’ve heard that some ergonomists recommend using the mouse left-handed because you don’t have to reach as far to get to it (no numeric keypad to reach past).
GT
Left at home, right at work. My desk at home is set up a little weird.
I do both left and right handed mousing. At the same time.
I worked in a network operation center and had 4 'puters at my desk. It didn’t take long to become mouse-dextiorus.
Now I have two computers and use them both for different tasks.
Slee
Same here.
The upshot of this is that I can play video games fine left handed but not with my right. When I need to do something productive, like photoshop a picture, I have to use my right hand–using my left feels awkward.
I operate the mouse with my right hand. JUst gave it a try with my left and it felt weird.
Write lefty. Eat lefty.
Belt lefty. Tie lefty. Watch righty (ie: left wrist).
Bat righty. Scissor righty. Mouse righty.
Photoshop, Illustrator & all other graphic tools righty. Draw lefty.
My mouse is on the left. I eat with my left hand. I wear my watch on the right wrist. I can write with my left hand if I want to, but not as well as with my right.
The greatest advantage to having the mouse on the left is that I can use the mouse and the keypad at the same time. Not only does this save some movements when I’m number-crunching, but it’s indispensible when playing some video games. 
I’m right-handed, and at first i was going to say I mouse with the right hand only because of the way my computer desk is set up. Then I thought about it, and realized my trackball at home is also on the right side.
So I don’t really use my left hand much at all.
Write left, though I can right - just looks putrid.
Bat either way. I have more experience right, but more intuition left. That’s right, I swing both ways. I can eat with either hand, though I cut and eat with my left almost exclusively.
I operate a mouse with my right hand. Using it with my left hand feels much like writing with my right in terms of dexterity.
I usually use my right hand but sometimes I’ll switch to my left hand if it’s more convenient (like if I’m sitting off to the right side of my desk demonstrating something to someone).
I’m a rightie. Wife and kid are lefties.
Left mouse at home, right mouse at work.
No real difficulty.
Also right-handed, and always use the mouse left-handed. I do, however, reverse the buttons.
The reason I started doing it that way dates back to my first job with a computer, where there wasn’t enough room on the right hand side of the desk for the mouse - hence, I used it left-handed.
Afterwards, I couldn’t see any point in changing to right-handed, since it’s really comfy in the left hand and it leaves my right hand free for the arrow and number-pad keys (really handy for games like EQ and other computer games with arrow-movement).
Ohh! Me too! It used to drive my mother crazy that I set up the ironing board backwards, and she tried to explain to me why it was backwards several times. She never did understand that I ironed left-handed.
I also prefer to use scissors with my left hand, given my druthers. However, since technology really hasn’t perfected left-handed scissors (and I can never find the one pair I own that actually do work), I generally use my right hand instead.
I can mouse either way. I used to do a lot of PC user support, and pretty much got used to whatever pointing device was on the computer I was using, on whichever side it happened to be. My right-handed daughter insists on putting her mouse on the left side, with the buttons reversed, for her own computer, so I’m even used to that now.
My preference is my right side, but that’s mostly out of habit, and because I use my left hand for Ctrl hotkeys quite frequently. I use a laptop most of the time, so I keep the mouse on the right side, and the USB keypad on the left side (and I can ten-key with my left hand while I’m mousing with my right hand).