PC, can't speak to the PEC ATL events directly, mine have all been here in Germany at PEC Hockenheim and Nurburgring. I would echo the statements from all and include my general commments:
1. driving sessions on the dynamic sections (skid plate, slalom, advanced braking, etc.) were extremely beneficial to see how your model reacts
2. instructors are different and come with different strengths and weaknesses, but all are professional and know the vehicles
3. being open about your driving skills and what you want to get out of the sessions will really help (be prepared for some honest feedback)
4. recommend going with as close to your model as possible if you are not bringing yours, if you want to see how yours will handle (I know not all can do that, I am very fortunate living within short drives of multiple PECs and tracks)
The 'worth' can only be determined by you, but no one is ever going to lament having spent time at a PEC in a Porsche getting faster.
Enjoy whatever you do, take lots of photos, and have fun!
- Oz