I owned the Acase and Wacom Bamboo stylus pens for tablets. I gave the Acase to my sister and bought the Wacom. Although to be honest the quality and performance were nearly the same. These stylus tip is 1/4" diameter. The tip is like a rubber ball that deflates and allows you to apply pressure and you move pen across the screen.
After watching the videos of the DAGI stylus in action, I bought it (although the HTC model appears virtually identical).
I don’t do a lot of drawing, but that is what these style of stylus are designed to be best at. I do use my DAGI for handwriting input (PhattWare) and some limited drawing, and it does work quite well.
I also have some of the rubber bulb tipped styli, although I find that they seem to drag along the screen surface for any sort of action which requires more than a few millimeters of on-screen surface movement (like writing, and drawing). But, they do work nicely for simple "touch/press" type operations.