It's interesting that people almost never disagree with this when they're the customers. We love seeing progress, even if it's a small portion of what we need. When frequent updates show that progress is slow, we're glad we're aware, and we don't blame the updates themselves for slowing the project down. In the rare cases where we feel like the process demands too much of our attention, we don't stress about it; we just say, "Looks great. Let's talk again in two weeks or when you have completed feature X."
Those hypothetical drawbacks only loom large in our minds when we're the ones doing the work.
What about those invisible people who gave it a try and decided there were just too many gaps and bugs? They are not customers anymore and probably never will be.
When the only way to get feedback on something is to go live to random customers, yeah, that's a difficult decision. I was thinking of situations where you are getting feedback on pre-launch software from a customer or from your own product organization, or you have an established product and some of your customers opt-in to beta functionality because they want the opportunity to influence your direction. I agree there are situations where the worse mistake is giving people a bad first impression.
Those hypothetical drawbacks only loom large in our minds when we're the ones doing the work.