I'll start by saying the store is a complete zoo. Avoid nights and weekends, if possible.
I made an appointment online and checked in when I got there. After waiting 40 minutes past my appointment, I asked if I was close to the top of the list. The lady said I was almost next, so be patient and someone will come over.
It wasn't clear who was going to help me or how many people were waiting, but eventually (about 50 minutes after my appointment time) Darnell came up and checked out my phone. I was having trouble with the battery and needed a few accessories. He ran a utility that showed how robust my battery was showed me the little graph. After reviewing that my battery wasn't great, but also not terrible, he recommended I hold off on the $85 battery replacement and wait for my next upgrade.
Darnell provided some awesome advice, but I felt like I had to beg for any kind of help. Why do they use the appointment system if you end up waiting anyway?