The manual mentions that auto focus may not work with
slow shutter speeds, but doesn't specify what speeds.
I was messing around at 1/30th second the other day
and it seemed that it was slower than usual to lock
on focus (i.e. more hunting) as compared to 1/60th second. Is this just my imagination?
Has anyone else noticed this?

That's interesting. Wonder if it's because there are only half as many scan lines available when you drop below 1/60?