in my opinion, to get useful feedback, you need to actually release something. Specially for modules related to some specific field, say bioinformatics, its much easier to get bioinformatics to comment on your module if you give them some working code.

If you start with a complete API doc, but without code, then you will get feedback but more of the "teorical" kind... and then you will need to discern the good advice for the bad!, with working code you can just try and decide... thought, obviusly, you should be willing to change things.

Be realistic, you don't upload a module on CPAN and zillions of people start using it, and anyway, most people will expect a module at version 0.01 to be unstable, and will not complaint about API improvements.