My two cents.
Well, I don't see why you have to do "double the work". To me it depends on what you want to do... Do you want to be able to pick up a paper or what ever else is handy to create a cool drawing? or do you just want to make "cool" drawings on the computer and that's it?
To me, you can use what ever tools you like. There are some people who draw great with a graphite pencil, but if you hand them a piece of charcoal, they are lost. Granted, if their fundamentals are good, then it will only take a little time for them to get accustomed to the new medium and produce good drawings in no time at all. I don't see why you can't start with a tablet first. After all, it's just hand-eye coordination. It might actually help your hand to eye coordination, because you aren't really drawing directly, but you're mind actually has to compensate for the difference in size of the monitor and the distance of your hand to the screen. I personally love to draw "organically" and would love to pick up anything that makes a mark and draw something amazing. For example, draw someone's portrait on a napkin using ketchup as the paint and maybe a french fry as the pencil? For me, digital drawing allows for too much "cheating", where the "artist" just takes a photograph (usually someone else took) and traces and uses the color picker to choose the colors. However, it's extremely easy and fast to create and distribute images and this makes it a great tool to learn color and composition. You can move things around and arrange things easily.
Anyway, if you are concerned with great pictures. I would suggest learning color theory, and fundamentals of good composition and lighting. Those apply to any medium you choose to use. Pick up some good books and study the masters.
Draw "organically" because it's fun, and portable, great practice, and it will impress your friends

but If you want to be the best digital retoucher out there, don't delay, start using the medium that you will be ultimately using. Why delay, the sooner you start the sooner you will master it.
I hope I made sense. It all just came out like some sort of exorcism