We have been using Kindles for about two years. We host a State level match once a year and use the kindles for our monthly matches as well. We have experienced some issues that I can share.
1) heat- they heat up and quit working when the OA temp is above 85 or so. To mitigate that we have the squads keep them out of direct sunshine and close the cover between stages. It is amazing how doing these two steps makes the devices run better and longer.
2) WIFI- after we do our initial sync and before we distribute the devices to the stages/squads we turn on "airplane" mode. This saves the batteries and allows them to work for a full day. We have 10 devices and I think we have a couple that are starting to have battery life issues, due to poor management techniques early in their lives.
3) Sunlight- This is the bane of our existence. In bright, direct sunshine they can be hard to read. Especially with polarized glasses on. It seems that some eyes are better than others but again, creating a shadow with your body seems to be enough to allow them to be used.
We have borrowed another clubs Nook NST and they worked great, but still have occasional issues.
Overall, I would say that a little education goes a long ways towards making people comfortable using anything that is new.