What this product claims is you'll be able to make fancy filled cakes quickly and easily. It comes with four pans to make two different shaped cakes (a dome cake and a more traditional layer cake shape) and a booklet of instructions and recipes.
If there's a trick to using this set successfuly, it's in following the instructions exactly. You must use shortening, not cooking spray, to grease the pans and fill them precisely. The only time I've had a bad cake was when I mis-measured making the cake batter and it overflowed the pan. I've made ice cream cakes and cakes filled with puddings or fruit. Ice cream cakes are probably the most time consuming, as you have to soften the ice cream just right and pack it in carefully.
For my birthday cake I used a devils food cake and sugar-free white chocolate Jell-o pudding (sugar free because I couldn't find it sugar-full!). I wanted something like the creme they put in creme-filled doughnuts, and this was awful close. In hindsight I bet my Safeway bakery ladies would have sold me four cups of filling.
I used the round dome cake pans and the pudding-filled cake guidelines in the pamphlet. I should note that the recipe calls for one box of pudding, and this took two. You make the pudding with a half-cup less milk like you do for pie, for a thicker set. I also used one chocolate pudding cup for a dollop of chocolate in the middle. If I had a little more time I would have made a chocolate ganache and poured it over the top of the cake for a chocolate overload!
With the inside so fancy I kept the outside plain. My camera ate most of my in-progress pictures and a lovely pic of the just-cut cake (I finally contacted Kodak to troubleshoot that, shouldn't be happening any more), so you'll have to settle for a "before" and some half-eaten shots.
Final review: It works as advertised and I get very nice results. You'll find your cakes a little more dense than you expect if you're using pudding cake mixes: this is in part because you have to refrigerate or freeze the cake and part because the pans restrict the rise for a firm cake that won't collapse from it's own weight. You will want to give yourself a little extra time to make the cake (maybe start a day ahead), for filling and chilling or freezing it before serving, and don't forget to make room in the fridge or freezer before you start. Overall two thumbs up and a product well worth buying if you like making fun cakes.
PS: Surfing around looking for links for the Bake 'n Fill set, I discovered Betty Crocker also makes a mini-cake version! Based on my experience with the big one, this is going on my list!