Paying a 'professional' to review my SaaS product?

I have a fairly narrowly-targeted MVP that I aim to release as a SaaS product, soon. It will be targeted at web developers, bloggers, or even just people with tumblr pages. It will come with an API, JavaScript libraries, and documentation.

I've never released this sort of product for this type of market before. I want to have my design and functionality nailed down, well before I release, so people take me seriously.

How would I get people who are very experienced in these markets (like many of you) to critically review this, beforehand? Is there a service that lets me pay experienced professionals for review?