You can draw some very good curved lines with your mouse and the Draw tool in Paint Shop Pro 7. Click on the Draw tool and go to the Tool Options Palette. Then set the Type to Bezier Curve. I like using this Bezier curve tool instead of my graphics tablet.
Some digital artists really like their graphics tablet and others do not. I have used the mouse so much that I can get great results with just my mouse. I think that practice is the key with or without a graphics tablet.
Hope this helps,