I do it all the time. While I'm not seriously looking, I hate the house I'm in now so you never know. DW likes to go to get decorating ideas.
I've sold two or three houses where we had open houses. It was understood that a major demographic visiting the house would be "nosy neighbors." Nothing wrong with that - you never know when somebody will have a relative or friend causally mention they're looking, and the looky lou's might recall seeing the property and pass the word.
Besides, I've had at least two of my houses sell either on the day of the open house or within a week to someone who came to the open house. That was a different market back 10-15 years ago, but it happens. I wouldn't count on it in my current market.
Nothing worse than attending an empty, open house. My immediate reaction is that the owners must be motivated if not desperate to sell. I really don't know that and it's not fair to think it, but it's always the first thing to come to mind.