Compared to XP or anything from Microsoft, iOS is the most stable of them all.
Might be, however iOS inherently allows a lot of end-user input. XP can be configured to prevent that and only allow whatever the administrator wants you to use. If those PCs are not connected to the internet then there is no real danger. Our windows EFBs only use an airline programmed UI, there is no possibility to get into windows itself for the normal user. Only thing i don't like about that installation are those damn military grade tablet PCs that are real heavy and have a very bad input technology.
iPads are nice to work with of course, however the software issues can be a real headache. There is no single point update so each app and the OS have to be updated separately and each possible combination has to be thoroughly tested with usually means that approval to update the OS version can sometimes take a long time.
Can you use the AC charger that comes with the ipad or does it have to be something that is aviation certified?
It works, if it is approved depends on your specific aircraft installation.