Drupal 7, Paypal integration with registration form

Hello there,

I have a web application built on Drupal 7, that I want to sell over Internet based on a monthly subscription fee. I mainly want to integrate Paypal with the registration form so users can pay when they register.

Accepted payment is going to be credit card only. Therefore I want to display credit card fields inside the registration form, and start charging monthly based on the plan the user selects.

So briefly what I need is:

Recurring payments or monthly subscription.
Credit card validation on registration form ex: http://bit.ly/vyMkkL

I have tried several modules such as Ubercart and Commerce, they seem to be much bigger than what I want and unfortunately they don't seem to be stable enough for Drupal 7.

I would like to know if there are any suggestions for better approaches to accomplish what I need.

Your help will be much appreciated.