So, 18 hours later, my third Pfizer dose made my arm sore and disrupted my sleep a little. Otherwise, no side effects.
Updates as conditions warrant.
Update: OK, there's quite a bit of fatigue. And a bit of headache. No fever, though; I'm at 36.9°C, which is the high end of normal for me at this time of day. CDC says it's OK to take an ibuprofen after the shot, so I will now do so.