For $50 a table, unlimited badges, and free general attendance this convention is very worth it-- but mostly if you're a San Antonio local.
The venue is a very unique spot and the layout can be difficult to navigate, but they do provide in-depth maps by area with numbered tables and artist names to make it much, much easier if there's someone you're looking for. Because the venue is inside a mall, there's a unique array of stores (including a Target! which can be a life saver), and there are more establishments surrounding the mall if the food court doesn't do it for you.
The convention does require you bring your own table and chairs, which is why I would not recommend heavy travel to do this convention. Definitely don't fly out, but it could be worth it if you live within 2-3 hours and are willing to make a road trip. Set up finishes at a very late 12 pm and ends at an early 7 pm so it could be a day trip if you want it to be.
Though the one-day event is sponsored by San Japan, compared to SJ's super strict set of rules Mini-Mini is pretty lax. Staff will check up on you maybe once or twice but they'll stay mostly out of your hair. I'm not even sure they checked for a Sales Tax ID.
Because the event is free to the public, attendance is much better than you'd think. Most of the day I couldn't see the tables across from me and I was kept busy with customers, walking away with 10x the amount I paid for the table. The event is 80-90% ABOUT the artists, and people come very ready with money to spend.