I, too, love the challenges. It does indeed stretch my skills. when I see what others have done in the same challenge the little light bulb of "ah ha" or 'hmmm' goes off.
One of my guild's last challenges was to use a certain amount of the fabric given and use as many different fabrics with it as possible. the winner did a beautiful scrap quilt with about 75 different fabrics, which she documented. it was bresutiful!
Now I wnat to do a large scrap quilt too.