Well, it went OK, I think. They had me come in and call songs (chosen from the band's existing book) for an hour-long rehearsal. I made a couple of mistakes that I shouldn't have, successfully pulled off a couple of tricky bits that the others didn't seem to expect, and was able to do some background vocals, which they'd said would be a plus. Fun was had all round, I think, which seems like a good thing.
I know they're auditioning other people, but I was introduced to the owner of the practice space as "the new bass player". Not sure how seriously to take that, but it does sound like a good sign, doesn't it?
Pro tip: When your hand lands on the wrong string, and you end up playing a perfect fourth instead of an octave with the rhythm guitarist, you can make the drummer get a really impressive facial expression as he gets caught in between the two notes. Oops.