hmm it all depends on what you want to do! If you want to do more digital art, then its much more convenient, you can do all your lines and color them directly on your cpu without scanning the sketch and then digitally rendering the lines so they're clean enough to start coloring on it.
I think one of the "cons" of tablets for first-time-users (i.e. me! hahaha) is that we need to draw on the tablet while looking at the cpu screen and make the mental connection as to the location where we're setting the tablet pen on and the screen point we're targetting! But of course, this is just something we learn with time, once we get used to it, it's like learning to ride a bike
you hardly need to think about it to go where you want.
But if you are like me and are unsure of your brain abilities of aquiring this new visio-motor skill, this is where Wacom's hyper-expensive Cyntiq tablet comes in handy: built in screen on the tablet. So the tablet become your paper, or a part of your cpu screen - you draw on the tablet's screen and you see directly on the tablet what you draw. But a 12inch already costs $1000 - Hyper-expensive hyper-sensitive tablet indeed.
One "pro" for tablets that applies entirely to my case and probably 30% of the tabletless artists out there: when I color digitally my art, I have to use the mouse. I am left-handed since birth, but I have only learned to use the mouse with my right hand (never got around to getting a left handed cpu mouse).. so it's always a headache when I need precision in coloring! haha! Tablet solves this, magnificently!
Goodness! I sound like an advertisement for Wacom hahahaha. (I PROMISE I AM NOT!!!) I am thinking of getting the Cyntiq though.. since I don't think I have enough brain juice to be able to use a screenless tablet. But these things are so expensive, I think it will be on my dreamy-I-wish-to-do-if-only-I-could-list.