It varies tremendously. As I wrote in a thread it can be non existent to mildly frustrating. I think the majority of mine is self affliction and anxiety as when I am drunk friends of mine have commented that I don't do it at all. It was much worse as a kid. Speech therapy helped me tremendously. I wouldn't advise using speech therapy, though, unless their stutter remains consistent into school time. With my daughter, as I said, just be patient and let them get out what they want to say while also advising they slow it down a bit if they talk fast like my daughter. As a person who stutters yourself, you know the worse thing a person can do at us is finish our thoughts/sentences. I hate it and it usually causes me to stutter worse. I also wouldn't bring attention to their stutter, even in a cutesy way. My girlfriend did that with our daughter as she thought it was "cute" and I had to remind her for the person doing it, it was never cute to us. Patience, slowing down their talking, and not putting a spotlight on the stutter I think are my best pieces of advice. Good luck.