Hey Christer,
If I use verified trials: It's a bit unclear to me if you must call the UseTrial() function or not.
With TurboActivate 3.x? No, "verified trials" in TurboActivate 3.x and older is simply using the product keys and custom license fields.
With the upcoming TurboActivate 4.x (and newer)? Yes, verified trials will be built into UseTrial() and TrialDaysRemaining(). We'll have documentation and examples that explain the new behavior when TA 4.0 is released.
Another unrelated question: A product key that has been revoked, does not count into my max number of allowed activations for my account? If I give out trial product keys, once they have been "used", I want to revoke them. I could "reuse" them for another trial customer, but that seems a worse way. Better then to create an entirely new key.
Currently "revoked" keys count against your total activation count. We're strongly considering changing that. Also, when TA 4.0 is released verified trials won't use activations.