Zack, what I am seeing now is that the conditional tags begin to error when adding more than one conditional tag. I installed the latest release and enabled just one conditional check for a tag, and it worked properly. However, when I added a second conditional check for another tag, It sets the tag no matter what the value specified in the conditional check.
Yes, I find this to be broken as well. If I knew php well enough, I would attempt to troubleshoot the actual plugin code myself. I have yet to find a fix for it. I also have the problem of tags being applied regardless of the condition I set.
Yes you can do that with a gravity forms hidden field. I do this for a survey I send out. Under the advanced tab for the hidden field you’ll need to check allow to be populated dynamically. Add the url parameter that will contain the email address.