Not at all. As long as you are showing googlebot the exact same content that subscribers see then there is no problem.
Cloaking penalties are almost always manual penalties. It doesn't matter how many complaints Google get. When the Google rep checks the site manually, they will see that you're giving Google access to subscribed content and not trying to cheat the search engines.
If you were to create new content just for the search engines and not your users then you will be in trouble.
A lot of major newspapers use this technique. I don't see any getting downranked because of it.