Writing non-trivial functionality in cmake's language is possible but you're fighting the language the entire way. It would have been so much better if they'd just started with something like Lua and extended it instead of building their own barely-adequate scripting language. Some of the grossest code I've ever written is in cmake macros.

On the other hand, the results you get from cmake are fantastic. Want to use ninja instead of make? Just pass a compile flag. Need Visual Studio project files? No problem. Xcode? Kdevelop? You're covered.

Honestly I couldn't imagine ever going back to autotools at this point.