I have a very detailed and extensive wrist bracelet. It was done over 4 sessions and took almost 13 hours.
It did not hurt much at all throughout, but what was a problem was that because it went all the way around, and swelled, the 1st healing was very difficult. It looked horrible for a good week, and I had to baby it like crazy. After that each session went much easier during the healing time.
Also, I wasn't as savvy on taking care of it as I later became, so I would like you to learn from my experience.
Make your placement up past the wrinkly part of your wrist (by the palm). This skin is thinner and will twist and pull and stretch with every movement of your hand.
If you have any images (like a flower, animal, figure etc.) that has a top and bottom - place the 'bottom' towards the ground when your arm is hanging at your side.
While healing, keep your hand and arm as still as possible, .. pretend that it is broken and use your other hand.
If you have much detail, make sure to ask for a 'fine line' needle, to keep it delicate, and this will also help keep the lines further apart so that it will hold up well over time and not blur.
Wrist tattoos can be subject to line blowout if you aren't very careful with the healing.
Use current aftercare methods. Do not use heavy ointments, or Neosporin, no petroleum or lanolin products, no dyes or scents.
Lubriderm and Curel are the best from start to finish - apply a light coat, do not smother.
Do excellent aftercare 3 - 5 Xs a day for as long as it takes to heal.
Pat off any seepage/ink transfer whenever you see it to avoid scabbing (which can pull out color).
Here's an excellent video explaining current aftercare methods:
http://www.youtube.com/watch?v=DXS9t1Ec7pY
Think your design through, and draw an idea of it in the proper size on your wrist and move around with it. You will be amazed at how the skin position changes and the placement of the image will move around. You must take this into consideration. The image needs to be placed while your arm is hanging straight down at your side, with your palm next to your body, to be centered properly.
Don't worry about the pain of getting it. Worry about your images and idea ahead of time, and your aftercare once you get it.
Wait until you are without doubt about your idea before proceeding. There are always surprises. I thought I had worked out everything, but after the initial tattooing, I realized that it looked more like a watch than a bracelet, and had to rethink my idea. But the end result is fabulous and very unique and meaningful. But much much thought went into it.
luck~