Often, I had to log in to the site multiple times in order to access whatever information I was looking up. I'd log in, then go to the class or game list or whatever, and it would decide I was not logged in. It is not obvious from the landing page you end up on after logging in how to get back to the ReaperCon event pages and have the system continue to consider you logged in.
When submitting events, either classes or games, it's just good practice for the confirmation email to contain the details of what was submitted. It should include the content entered into every field on the submission form. The confirmation emails from GrowTix have just the name of the event and then the generic ReaperCon text.
When submitting classes, there were fields to fill out that included things like what level a class was intended for (beginner, intermediate, etc.), whether it was going to be a lecture/demo or hands on class, and skills that a student should already have in order for the class to be most useful to them. This information was not visible in either the class listings or the detail pages for classes, and it should be.
As an event runner, it would be useful to have events you are running, whether they be classes or games, show up on your schedule.
Treating classes and games as completely different entities causes problems later when somebody is trying to figure out what their overall schedule is. It would be better if it was just one list of events that included everything available for registration.
The overall usability of the site is very bad. If you have to provide detailed instructions and walk-throughs on how to perform tasks that are the primary intended use of the system, that is a usability failure. If the purpose of the site is to allow people to enter events, buy badges, and sign up for and purchase tickets for those events, it should be designed such that it is obvious how to perform those tasks successfully. It should also provide feedback that clearly indicates what your status through that process is - whether you are actually registered for an event or if it is just on your 'wish list', etc.