After some initial hickups I have finally integrated ClickandBuy into Magento. Integration was done for Gelaskins-Deutschland.
Sadly the documentation was hardly a timesaver, as it is either out of date or incomplete.
I was able to get most of it done by knowing the Zend framework, reading the phpdocs, reading other modules and browsing this forum alot, but that is hardly the perfect way to get any developer working with Magento.
If I find the time after my vacation I will write a small summary of a quick and dirty way to get a payment module running.
Thanks for a great shopping solution, that many of my customers enjoy.