I agree with IO540 on the whole.
For some reason, the iPad seems to me to just feel "not suited" to air navigation.
It can physically do it all, AirNav Pro will run UK charts, and as long as you're happy with north up (which I personally am), they're completely fine. As IO says it's great as a doc reader for plates, etc.
But somehow it just doesn't feel solid enough.
The visibility I also concur is pretty poor in the sun - something I guess it's just not meant for, and there is a polarisation issue if you wear polarised glasses, depending on which orientation you have it.
It's too big to be mounted up high, and too difficult to use mounted on your leg (again, just in my opinion).
But I will say that I've had mixed experiences with the GPS, and from my experience it may work fine in your aeroplane (As I've seen it work fine in some), but in mine it doesn't, and loses position fairly regularly - probably would be fine if mounted high?
The apps you need to make it work fairly well are pretty expensive, but most of them have a free version to allow you to trial them.
I certainly wouldn't buy an iPad to use as an in flight tool, but if you already have an iPad you owe it to yourself to try it out at least.