I agree with your comments on asking for credit card info upfront. As a user, if I were to try out a 30-day trial offer, I'd prefer to provide my credit card info after the trial ...and only if I decided to purchase the product.

I recently purchased HttpScoop which uses this model (great product for the Mac and they let me try the product for 15 days before asking for my credit-card info) --- As a developer, this is the model that I'd use for any of my products that have a trial offer.