Can it do everything a regular stylus can + obvious advantage of the rotational brush?
Why would someone prefer a regular stylus over the 6D art pen?
I need to get a stylus for the Wacom/Cintiq class I am taking. I am real novice at using the Wacom. I think it might be easier to make the transition using a 6d Art pen as it can mimic a chiseled edge drawing tool.
First things first, and my main criticism: The art-pen has no rubber coating, which means it's a solid, rather thick piece of plastic, that will probably hurt your fingers after an hour of using it. You can use your own foam-coating, but that will make the already big pen even bulkier. What I like about it though is that it's shorter than the regular pen (As you can see, the new, black Intuos4 pen is shorter than the old Intuos3 pen, which was too long to rotate it properly)
The rotation feature is a nice marketing feature and probably the reason why Wacom is still selling the pen. But with CS4, which now supports GPU-accelerated canvas rotation, you can easily overcome this by rotating the canvas instead of the pen.
Is the Art Pen useful? Yes, it can be. Is it worth the $60 price tag? No, absolutely not. You can get the same results with the (much better built) standard pen, I don't know of an artist using the 6D seriously in every day work.
I use one and I'll only recommend it to somebody who has Painter 11 (to get the full experience) and a laptop/desktop that has at least 4 gigs of ram.
If you're just starting out making art using a tablet the round barreled stylus should be enough.
And, far as I know, 6Ds aren't compatible with intous 4 yet (they might have upgraded the drivers already, but check on that if you want).
The problem under Photoshop is you will need to change the normal grip pen for the 6D art pen only for specific brushes (as the normal pen is better for anything else...side button, eraser) and you will need to change the brush also inside Photoshop selecting the one which will be able to use the rotation feature. That's mean it can slow down your workflow (changing pen+ changing brush) as it doesn't give you something impossible to do without it. Anyway, as you will use it with a cintiq, it can give you a more consistent way to orient your brush on the screen.
Under Painter IX.5, X and 11, as a complementary pen, it can give you access to a much better control of any flat brushes or any brush you need to orient precisely. It can give you access also to bristle brush twisting like you can see in this video
And as Painter uses the Wacom ToolID (unique identity per pen), Painter can remember which pen was using any brush, so you can work with multiple pen without the need to think about changing the brush when you are switching for another pen. I need to add also there are still brushes in Painter 11 you can't orient without the 6D art pen as the normal bearing setting cannot be set to those brushes.