The first stage is just getting an offer to attend a hiring event, Apple receives A LOT of applications so it may take several tries just to get through to the first step. The hiring event itself is a great experience where so many unique and interesting people are put into one room. It can be intimidating though and you really have to make yourself heard and stand out from a large pool of qualified candidates. About 150 were invited.
The second stage was being invited back for a smaller interview, I heard back the same day as the first stage because the second stage was the next day. They cut it down to 32 for this particular event. They had 6 people per group and split it into 3 and 3, you then went into a room for a half hour with one panel and then switched for the latter half of the hour. The panel is kind and really encourages you to shine bright. The others I interviewed with were such amazing people, don't get intimidated by others just continue being yourself. The panel thanked us for our time and said we'd hear sometime next week, I heard the next day.
The third stage was another interview, but this time actually held at the store and it was held about 3 days after the second stage. This stage had been cut down to 12 and the interview was for groups of 3. The entire hour was similar questions as before, but this time you are interviewing with store managers and other higher up management. This is the interview where you feel grilled because they are coming down to their final decisions. Nothing is definite, but they do tell you that if you make it down this far you are put on their "bench" if you don't actually get the job, which means you're basically hired with an indefinite start date.
I heard from them 3 days later with an offer and I accepted. Apparently only 6 positions were open at the time and as positions open they will pull from their bench. It was overall a great experience and I'm not just saying that because I received a position, the interviewing process is fun and you meet a lot of great individuals.
Sidenote - there are no traps that they lay out for you, they do not judge you by where you sit or how long you take to answer or if you need to excuse yourself for a drink of water. The "trick" is to be outgoing and show them that you are someone who aims to succeed and that you are committed to helping those around you better yourself. Don't sell yourself short, give unrelated answers, or waste their time. You are playing with the big dogs and you have to present yourself as well as you possibly can.