These great machines allows you to edit your photography on the computer using Adobe Photoshop. They allow editing whether it be taking out the background and adding a black n white themed effect.
Personally I find them a very useful tool and defiantly any photographer should have without a doubt, as they are becoming far more accessible as the price becomes lower.
Well, that's not exactly what they do. They basically replace your computer's mouse with something shaped like a pen and paper, making it simpler to do artist work on the computer for people who prefer traditional methods.
My parents gave me one in my early teenage years but I was an idiot at the time and it got broken somehow (don't remember how). What sucks is that I now want one so that I can do proper illustrations and stuff on the computer because I love drawing freehand (basically the only way I can draw).
As for editing photos, I probably wouldn't use one for that. I'm too used to using my mouse!
I wonder if the iPad will replace traditional graphics tablets in the future. There's already lots of iPad-made art out there, and just recently I remember reading about new styluses coming out that would make it even easier to draw on an iPad.
Not yet, the iPad screens aren't sensitive or precise enough to replace a Wacom / graphics tablet. However, the Samsung Galaxy Note phones and I *think* the Samsung Galaxy Tabs both use Wacom screens, so they are effectively graphics tablets themselves.