I can tell you that the Mighty Mouse is actually fairly comfortable.
I've got very badly damaged hands with torn tendons and other issues (plus arthritis).
And, with some mice, I can't click but one time before my hands are totally incapable of continuing. Likewise, I cannot type on a straight keyboard without suffering quite a lot. What I've already typed would finish me for the day on a regular keyboard.
So, for me, I was quite surprised to find that the Mighty Mouse would not hurt my hands. Admittedly, I probably didn't hold it the same as anyone else would. But, I was able to hold it and use it without incurring any pain at all. Not that I held it weird. Just that my fingers may not have been exactly where someone else might place them.
The only reason I don't use a Mighty Mouse now, is that I got tired of scrubbing that annoying little ball. It was fine for the first 6 months. But, then it got to where the oils had built-up and it wouldn't scroll one direction or the other. So, I'd have to spend 10 to 20 minutes scrubbing and rolling the ball with cleaner to get it not only working but also rolling smoothly again.
The problem, is that you are actually touching the rolling surface that makes contact with the sensors internally. So, as oils built-up, it begins to slip past the sensors.
And, while getting it to work again was a minor cleaning, getting it to roll as smoothly as it did originally took much more work. I would spend so much time cleaning it, that it began to frustrate me.
It made it 6 months or so without any cleaning. Then, it needed cleaning about once a month. By the time I quit using it, it needed cleaning weekly. And, I just didn't have 20 to 30 minutes a week to spend on cleaning a mouse ball.
So, I cleaned it one last time, and handed it to my wife to use with her laptop (she doesn't use the scrolling ball anyway).
The traditional mice, use a scroll wheel. Those wheels differ from the ball that Apple uses. The wheels spin on an "axis" or essentially and "axle". So, you spin the wheel, and it's attached axle rotates. The sensors on the axle. So, your finger oil never actually gets on the sensor surfaces.
So, when I chose to replace the Apple Mouse, I looked for something that would fit my hands very comfortably (by trying them in various stores), and also offered the full functionality of the Apple Mighty Mouse.
I found that in a Microsoft Mouse. Specifically, the "Microsoft Comfort Optical Mouse 3000".
This mouse uses a high definition optical sensor (for regular motion). So, I don't experience any of the jumping around that I got with the Apple Mouse (where my pointer would suddenly jump to the top left of my screen in the middle of moving something around).
And, it has a traditional scroll wheel with a little trick. In addition to scrolling, it will "tilt" left and right for moving left and right like the Mighty Mouse would if you scrolled the ball left or right.
Additionally, it has a single button on the side (left side) that is in a convenient spot for use, but not easily bumped on accident. So, I have the programable "4th" button that the mighty mouse features (it's side buttons) without the constant aggravation of accidental activation that I had with Apple's Mighty Mouse.
And, it has a very ergonomic and very comfortable shape that allows me to use it all day long in comfort. It is actually comfortable to hold and rest my hands on. So, not only does it not hurt my badly damaged hands, it also is quite comfortable to hold.
And, to give you an idea of how easy it is to aggravate the nerves and damage in my hands, I'll give you a few examples of what will cause significant pain:
Clicking a single time on a poorly shaped or sized standard cheapie mouse (like the Microsoft "Basic" Mouse".
Typing about half a sentence on a straight standard keyboard.
Turning a screw about one turn with a standard screw driver.
Pounding a nail in with a hammer.
Cleaning the snow off the car's window (unfortunately, still have to do the rest of the car).
Essentially, my hands are shot after using them for 10 to 30 seconds with any standard tool.
So, I have to use something unusual or custom for just about every job that requires use of my hands.
It's an unfortunate consequence of holding manual labor jobs as a teen and early adult years. And, of course the manual labor around the house as a kid and teen (such as in the landscaping work and digging and such that dad always wanted done but didn't want to do). When you use your hands to move things that weigh significantly more than you do as a kid, that's not necessarily helping things.
Over the years, I've torn just about anything that could be torn in my hands. And, unfortunately put an end to my hopes for an automotive related career (since I could no longer use the hand tools).
I've never had any repair work done on my hands, wrists, forearms, or fingers. I've always figured that the arthritis from the surgery would essentially place me about even. That's what's happened to most that I've spoken with who have had repair work done. Usually they got arthritis issues soon after that were worse than the original problems.
Or, like another I know, he ended up getting work done on his wrist. Then, due to complications, they had to redo it a few times. Then, in the end, they ended up having to essentially plate or lock his wrist in one position. So, rather than live with the discomfort he had, he now has to live with being unable to bend his wrist. Try doing something useful with that.
Take care of your hands. I know I'll spend many more years wishing I had.
Anyway, I say all that to give you an idea of how I base my judgement on computer accessories. I make my choices more on what doesn't hurt my hands than anything else. Obviously, lack of pain contributes to comfort. But, then there is general comfort as well that does factor in there as well.
For the record, I am currently typing on a Microsoft Natural Ergonomic Keyboard 4000 and using the Microsoft Comfort Optical Mouse 3000.
As keyboards go, the one I'm using is probably my second favorite of all time. The one I really liked was the very first Microsoft Ergonomic Keyboard (from about 10 years ago).
My next Favorite was it's slightly smaller replacement, the Microsoft Natural Keyboard "Elite".
And, finally this one that I'm using now.
My only complaint with the current one, is that it requires a bit heavier touch on the keys than the original two that I used to use.
But, all three enabled me to type without great pain. If I were typing this on a standard Apple Keyboard, I would seriously have stopped after the first 5 or 6 words.
Hopefully, my recommendations or comments will be useful to you.
Personally, I would suggest you make your buying decisions like I do. Go to the various stores, and actually hold them in your hands. Use them a bit, and try them out. See what you think of them.
For mice, if they aren't on a computer, but on a shelf, then set hold them and move them around a bit and see how they feel to you. Best Buy usually has several on a shelf with their cables tied to the shelf for you to play with.
For the Apple mouse, go to an Apple dealer, and play with it.
Make your final decision after you've sampled several.
You may disagree with my preferences. But, either way, you should only purchase after you've physically held and used several of them.