I don't think any tattoos are unbearable but that all depends on how well you handle pain. I don't have one on my wrist but the skin is pretty thin in that area and not much fat so I'd assume it would be in the top list of tattoos that hurt the most.
It's not an unbearable pain. It's more like a slow tortuous pain. It grows in intensity with time.
I very much doubt many people would have a problem with the pain. It won't last long and shouldn't have to many focused areas so that you'll be forced to take breaks frequently. I say if you want it... go get it done.
It's not bad at all. It kind of feels like cat scratches, to me, and afterward it's sore like a healing cut, but hot and aching like a bad sunburn. All in all, it's a pretty minor pain, especially if the tattoo is small like my wrist tat is. =]