Well I have just bought an I pad 3, after much deliberation. Went for Sky Demon, and have it installed on both I pad and home computer, have used the sky demon app on last 2 flights, and I am pretty impressed. I also have been using it without additional external GPS and have had no issues, although I have an external GPS pending on order, I will wait and see what issues I encounter. Initially I did not download to my computer, I did this retrospectively, and the whole package gives an enormous amount of planning, weather and Notam info.
I also considered purchasing other apps, but at moment cannot see what others may have over the Sky Demon product, without getting picky.