Decorators with arguments are much better handled by classes IMO. This does indeed appear to make that one (common) case of passing the function arguments through unchanged marginally simpler. But it makes every other case worse. Compare, for example:

    @decorator.decorator
    def int_args(func, *args):
        """Coerces any function arguments to ints"""
        return func(*map(int, args))

to your:

    @funcy.decorator
    def int_args(call):
        """Coerces any function arguments to ints"""
        return call._func(*map(int, call._args))

In the former case, everything is defined explicitly and it's clear that the function only accepts positional arguments. In the latter case, you're required to know the API of the library: that necessary objects are hidden behind the attributes call._func and call._args, and that the keyword arguments are silently discarded. It's an extremely leaky abstraction.

You probably think that passing 'self' to every method is boilerplate too, and arguably it is. But the Python philosophy is "explicit is better than implicit".