There are a lot of jobs that require dexterity. Athletes, artists, and musicians alike all require some level of dexterity to excel at their occupation... unless you play soccer and you're not a goalie but you know what I mean :)
In the jobs I've held in the past, I've never needed dexterity. I've always worked in an office. Peter Drucker called us "knowledge workers" in that we used our knowledge and our brains to produce services/services and/or facilitate the production of goods/services.
Photography requiring dexterity? Not so much. Anything with an opposable thumb can hold and push buttons.
Retouching on the other hand... very much so.
And so it dawned on me that some of us don't quite have that level of hand-eye coordination. That's it's hard to smooth out medium frequency skin tones with the dodge and burn tool. That the Wacom tablet is hard on the wrists.
I had forgotten about this. The dexterity required to get in some difficult spots to retouch blemishes came very naturally to me. It wasn't long before I was totally at home with my tablet. Now several years later, the tablet is the most important tool I use to create what I create. I've said this before but I could shoot on a Canon (instead of Nikon), use Aperture (instead of Lr), and Gimp instead of PS. I couldn't use a mouse or trackpad instead of my tablet.
What if you aren't comfortable with the tablet? What if you aren't blessed with as much dexterity?
Practice, practice, and practice. This level of familiarity come with thousands of hours of practice. It becomes second nature and it shouldn't be that far off from writing/calligraphy. The only way to get good at it is if you want to improve and constantly work towards a more refined product.
For what it's worth I use the small Intuos4 because I don't enjoy the extra real estate because I draw with my wrist and not with my arm.