I mean it's kind of pedantic but yes hash maps do have guaranteed performance characteristics. They are not guaranteed to be O(1), but they will never be something like O(2^N) either. You can give guarantees about their performance if you can make guarantees about the distribution of the inputs and the properties of the hash used.

In my own experience, most uses of hash maps are typically O(logn). A good rule of thumb is hash maps are preferable unless you need predictable worst case performance or your hash maps are directly exposed to the public.