MS - there are several threads on PPRuNe about iPads and their suitability as a nav aid. The iPad 3 is expected to be released (in the US) next month, but if you're only planning on using one for reading/surfing and maybe running nav apps, it might be worth waiting a few months and buying the current iPad 2 with 16gb. Prices are already dropping and will tumble once the 3 hits the streets :-)
PS you don't need 3G to use GPS