Quite frankly, for your money I'd really suggest that you'd consider buying a small Wacom tablet first to try out. Yes, Wacom brand, Graphire3 series to start. For around $100 you can get a small tablet and a copy of Classic Painter that comes with it, as well as a few smaller graphics programs. When you do that, you can then buy just the upgrade to the latest version of Painter (Painter IX (9)) and still use your Wacom with it, should you find that you really like the Classic Painter. And you'll get a better deal on the upgrade.
And if you decide you don't like the feel of the Wacom, or that Painter is not your thing, I'm sure you'd be able to find someone else that would be willing to take it off your hands.
For $100 it's definitely a cheap way to find out even if you enjoy it. If you do, you can always go on to upgrade to a larger tablet, and sell the smaller one as well or keep it as a spare.
I use the tablet in conjunction with Painter and Photoshop when working on my art. Not only for sketching out rough ideas but also for doing completed pieces. It's a bit of a learning curve, and I don't use the pen exclusively for everything, I'm not giving up my cordless mouse

. But once you do get used to it, you'll wonder why you ever attempted to draw anything with a mouse

lol. You can do more things with the pen than just graphics, its compatible with just about any program that requires a mouse (though, I don't really recommend trying to play games with it...not that I'd speak from experience or anything...but hey it gives you lots of practice with control...lol).
I find it an indispensable part of my computer setup.
Example of a piece done with the Wacom & Painter:

Detail of the image:

Obviously these examples show the more painterly side of Painter, but you can see the details in the brushstrokes. You just can't get that with a mouse IMHO.
Cheers,
Ivy
Edit:
Bec says put up something more hrm...manly
Here's a piece that I recolored, using the tablet and Painter. Original drawing not mine, it was originally a b&w drawing that I colored. It now resides on Bec's desktop

Ivy