I was going to avoid the 24HD because it did not rotate, but when I saw a demonstration, the guy rotated the screen image. I walked up to the guy and told him I'm a lefty too, but have a habit of drawing with the image almost completely sideways, he gave me a few tips and let me at it.... it felt pretty natural.
I agree, I don't think every designer needs one, some of the better illustrators I know still prefer the mouse. I would mainly use it to make my presentations look more organic, get my concept sketched in the computer faster, and the occasional illustration.
I think the IPad is getting to the point where I can use it for design so I'm getting it and running Adobe Ideas (
http://www.adobe.com/products/adobeideas.html). I tried that, and though not as tight as a Wacom, it does a pretty good job. They have it for Android devices too by the way, I would check out the videos...