Honestly, we did not think that people will use Sitefinity 3.0 in prodcution, being in beta stage. We do not recommend using our betas on production servers, as many things may break or change in the next release (as you have noticed).
The reason you are seeing these messages is because we changed the trial licensing, starting with r.a.d controls Q4. The new mechanism allows the development of UNLIMITED number of applications spread across various servers (and domains) without worrying about trial keys, which proved to be a hassle for most of our users. The only restriction is that you will get a trial message on top of the control occasionally when the control is rendered in the browser. Upon replacing the trial dll with the developer dll the trial message will disappear.
We are sorry for the inconvenience, caused by these messages. We will consider making them appear in a pop up window so that the design of your site is not broken.