Upgrades pluging

It would be nice if the was a $0 upgrade option. This way, I could set the 1 month option at $0 for some upgrades so a user can 'Try before you buy'.

I am going to be changing the 'Activate' option on some of my Themes to say 'Upgrade' which will let them upgrade to custom themes. I want to have the ability for them to play with the theme a bit before committing to upgrade. I would use this on other upgrade options, like galleries, video plugins ...

Thanks.