Spec has it's place, but I think people are trying to shovel spec in all sort of places; for example, heavy data parsing, making code very hard to track. Reminds me on core.logic movement couple of years ago, where everyone tried to have own parser/ui/whatever written in it, resulting very unreadable code.

What I'm really missing from spec is ability to disable it with flag or property, like "assert" macro. Sometimes I just want piece of code to run as fast as possible with less bytecode and instructions executed.