Interesting. I've only flown the classic Dash 8s and thought the autopilot was pretty good apart from a tendency to porpoise in a VNAV descent, but I did very few ILSs.
Same here. Never noticed the ILS issue in the 300. Just seemed to be a 400 thing. My pet theory (based on SFA knowledge) was that Bombardier had the same autopilot for the Q300 and the Q400, which then had issues managing a heavier aircraft. Come to think of it, the Q400 doesn't do a great job of turning the corner on an RNAV either. Never mind only having a 2-axis autopilot, but that's another story.
I do remember the porpoising (spelling?) on VNAV descents. Sometimes just went down in V/S to stop it.
JUDD, love the sarcastic comment!
DIVOSH!