I think they're okay. Like a lot of things they're of limited value and in many cases tend to happen when my sims are busy with something else or totally exhausted. One of my sims went to the flea market a couple of times and bought some junk, seems pretty accurate to real life. Romance festival is total fantasy but kind of funny, especially seeking the advice of the guru who tells you some rubbish about your future love life. Spice festival was good to learn the recipes. Never had a sim visit humour festival or geekcon.
Finchwick Fair is just as lame as the one we have in our village but one of the interactions makes me laugh "ask about bird's plummage history" or something. It is actually somewhat useful for loner sims to talk to a lot of sims at once, I never enter anything, I'm not into sim gardening.