First of all let me say that Blender is a truly awesome piece of software that I am very much looking forward to learning and using. It really is great!
One thing i’m having trouble with, however, is using the fill command (hotkey: shift+f) when trying to add a face to a series of vertices. For polygons with more than 4 vertices, I am aware that one must use the fill command which uses a combination of triangles to fill the void. This works on shapes with vertices around 6 or so, but if I try to use it on a complex shape, it won’t fill. Is there a limitation on the number of vertices or complexity of the shape that is stopping the fill?