I also sized up on the wrap shirt - I ended up going two sizes up because the one I wanted was gone when I got back to make my exchange. You can try it on there but you'll want to be wearing a closer fitting top like a tank or cami so you can get a good feel for size (I wasn't so bought one and they let me exchange it when it was the wrong size).
Some of the items will sell out quickly, and others they had lots of stock of. I'm sure it's all been posted here what went fast! They'll restock for 2nd session, but be sure to get there early! Since there are NOT limits for most items, and some demos have large groups they're buying for, it's just a good idea to get there ASAP!