We also wonder if these pans would be more trouble than they're worth. When making a frittata in a regular old pan, either you stick it under the broiler or flip it over to finish cooking. Using these Williams-Sonoma pans, you'd need to preheat the top pan so the frittata would continue cooking evenly when flipped. This could be an annoying extra step.
We do like the fact that the pans come apart, allowing us to use them for other kitchen duties. While the product description doesn't specifically state if the pans are the same size or not, they do mention using the top pan for crepes. This leads us to believe that the top pan is slightly more shallow than the bottom.