How or when to decide to use Invite Keys

Can't seem to find much on this topic, and I'm not sure if this is the right SE site to ask but here goes:

I'm developing an application/tool that I want to be really easy to use but also very powerful. Rather than open it up to the world for feedback which may or may not give me good data (or too much data for me to use), I've been considering the idea of giving out invite keys to select people in the industry to review the website and give constructive feedback.

Of course, I don't want to run into the Silicon Valley tv show problem of giving this to techs who are savvy enough to figure something out and normal people are left confused; I want REAL people to understand how to use the site too. I do have some UX friends I can invite as well.

What are your thoughts on invite keys? Are there situations where they work well? Don't work well?