I recently needed to build a site needing event registration. I needed to have nearly 1200 events programmed per year and decided to try Reg Pro. It crashed the site before I could get half the events in due to excessive memory requirements. Their support was at best ineffective.
I contacted Nathan who convinced me DT Register was worth a try. It worked great. The site is up and running with absolutely no problems. I can't say enough about the program and the support provided.