Another ex-Apple employee Genius chiming in.
First, as far as the multitasking, when I was there in 2004, we were already doing this. There was an appointment system, but not like what it is now. We generally took a few customers at a time, and there was never a time when a customer felt like I wasn't giving their issue it's full attention.
Second, if I was still working for them and read this, I'd be looking for a new job. The genii at the store are already overworked and underpaid. Now, they're talking about making them stay to work later hours to get repairs done. That doesn't sound good.
Also, while I was there I noticed a shift in how they were dealing with the Genius position. While I was there, we had quite a few sales people who were interested in advancing to the Genius position. While I don't have a problem with people wanting to move forward in their career, it should always be based on knowledge and skill set. Many of the people that I had to help train were not fit for the position. Not only did they not have the right temperament, but they also did not have the technical background to be considered likely candidates.
When I went through the interview process, it was three interviews. You had to meet with multiple sets of managers for the first and second interviews, and then you had to pass a technical interview. This was to make sure that people with right background were hired. When they started this whole promote from within idea, I can tell you, it left a bad taste in many of the fellow Genii mouths that I worked with.
Back in the day when the stores first opened, people were paid based on their level of knowledge and experience. So, Genii got paid rather well. Then, Apple decided to bring in some "experienced" retail people to corporate. That's when the changes started to happen in the stores, and they weren't for the better.
The problem with the stores and how Apple is handling them is this. They need to pay their people well, and treat them like the corporate employees. Until they do that, they are going to continue to have a high turnover rate in all positions, especially the Genius position, and will see a degradation in customer satisfaction.