I sent two very harsh emails to startups yesterday - both had solicited feedback.
The number one thing you have to bear in mind is NO ONE KNOWS WHAT YOUR PRODUCT IS!
You've spent the last few years living & breathing it, with people who share your vision. The average customer hasn't.
They take one quick look at your site, with its crazy name & inspirational logo. If they can't find what you you do & what you cost within a minute, they leave.
Don't be clever, or coy, or subtle.