While I agree with you about not supporting the people who steal, your analogy of the store is not correct. For instance, I can walk into ANY bookstore, peruse the books and open them up and read a few pages. I can then put it back on the shelf, no harm no foul.
I understand what you are saying but for me to pay 10 bucks for a book I do not know anything about is ludicrous. My favorite authors that I read? I pay for. Books that I "peruse" on the iPad then read? I pay for.
I also always pay for apps that I use. I may try an app ....
But to lay out 5 - 10 buck on an app that I have NO idea what it does or what it is like, well I don't agree. Screenshots look great, actual program is horrible. And the reviews are of no use, they can be faked. Offer a free "Lite" version or a time limited trial ....