The Genius tablet pen both work perfectly smooth. I am not into freehand painting, just done a couple of sketches, and looked good enough. As good as they would look with a pencil :)
With photoshop, the improvement is just great! For me it is much more efficient than the mouse. After a very short learning curve you are ready to take full advantage of the dinamics part of the tools, and you will be working faster and better with photoshop.