Hard to say exactly where the slowdowns were, but it seemed to be a bunch of things. The interview process took a bit longer than I'm used to -- they now have you do it yourself on a computer, which seems deliberately calibrated to be slightly slower than the usual in-person interviews. In general, they seemed very manpower-constrained: for instance, from the time I lay down on the table to actually putting the needle in my arm took 10-15 minutes, because they kept having to run off and deal with other problems. And all of it probably *felt* worse than it was, simply because they didn't have a good sense of how long the wait time would be, so they encouraged everyone to just sit. (Most of my co-workers sat for over an hour before being called, even if they had an appointment for a specific time.)
I appreciate the hard work that the nurses put in, and I'm glad to do it -- I never do manage to donate as often as I intend to, so having a convenient opportunity is a blessing. But I did find myself longing for the Children's Hospital bus at Arisia, which in my experience is a model of high efficiency in comparison...