I think I'd rather have separate devices for each of these functions.
This is my gut reaction too. Then again this was my argument against smartphones ... needless to say I don't have a separate Palm device & cell phone any more

.
I don't know if this is exactly the same, but I am seeing similarities.
Regarding maps, while I agree colour is a big question mark, I think the larger screen size is a big benefit. I don't find my GPS all that handy in showing me where I am in relation to the geography around me. I tend to use the GPS to find where I am on my paper map to get some perspective.