Ed,
The User Conference is sponsored by Navigator Business Solutions which is an implementation partner of SAP ByDesign. The conference is well organized and you will hear how different users from varying industries have implemented ByDesign. You will also get access to the Navigator team who has the most experience in North America for ByDesign implementations (sorry to any of the other implementation partners reading this but I believe those are the facts). You will find people who are still deciding on their ERP system all the way to the most experienced customers who have been on ByD since the beginning.
Deciding whether the conference is worth it may only be evident after you attend unfortunately. I am returning this year because the conference is probably the best place to get a high concentration of ByDesign expertise and real-world experience from power users.
Jim
Full Disclosure: We are a Navigator customer and they helped with our implementation. However, they don't tell me what to write about their conference...