I purchased this set for a birthday party I was throwing, and it is a very good combination, using the top, bottom and insert to make a huge cupcake!
My only quibble is that the top part cooks quicker than the bottom, and so you have to judge carefully when to remove each from the oven... also cakes need a LONG time baking - despite recipe instructions it has taken well over 80 minutes on occasion, to ensure the whole cake is cooked through. The cake comes out VERY easily from the mold - however I use a lowfat cooking spray on the inside, and dust with flour, before putting the cake mix in (just to help) and this seems to work a little better than just the cake mix on its own.
Make sure you have plenty of people to share the cake with - it really does serve loads - especially if you cover with yummy frosting. I took one to my works Christmas party and everyone was gobsmacked! Really worth the money. Consider buying a gym membership or exercise bike alongside this product... they can get addictive :)