But if needs are reading email, surfing the web, listening to music, or doing some word processing or other productivity tasks, where you don't need to worry about trading files with others then an iPad with the right keyboard can work well.
I think one needs to get some experience with an iPad before one can make an intelligent decision. Lots of folks have made the iPad their primary device, so it can definitely be done. But how you do it and how well it works depends on each person.
I should clarify. My use for GPS is a little unconventional. I use it for locating off road oil and gas leases. The "roads" that lead to them are a mixture of gravel, cut lines and ice roads. Not the kind of places you want to drag a trailer without knowing exactly where you are and where you're going.
For that reason I contend that the iPad is a serious work tool for me. We are not talking turn by turn guided navigation here.
I like the size, hardiness and convenience of my Garmins for driving. I sometimes use iPads for maps, but usually when I'm not driving and am looking up things for different uses.
I guess you must be fairly confused by now?
Thank you for all the thoughts. I must now agree we need both.