Assemblies were great when I was still going - well they were held at the home of football - Maine Road, Manchester.
Worst assembly experience is one I can't actually remember.
When I was 18 months old there was a large week long International marathon assembly at Wembley Stadium. Talks started at 9am and went on (I'm told) till about 7pm, with some old speakers waffling on for almost 2 hours.
Of course my family had to roomed (put up) near the stadium. For anyone who knows Wembley you wouldn't stay there if you were paid - it's the pits.
I got dysentry and ended up on a drip for 4 days back at a children's hospital in Manchester. Oh yes, many's the time we've laughed about this experience.
What a blessing such sacrifices were to the organisation !!