My experience is that Excel works fine up to around 100 odd test cases, after that, or when you have more than a dozen releases per year, Excel starts to drag you down big-time. It’s also easier to import Excel into any other tool, than to go between tools, and Excel actually lets you see your tests in other ways that fancy tools just cannot.
It’s a great tool to use for a few months though, because it might even prove that Traceability matrixes and test History and fancy features are not really as important as people say they are.