A few people who we met after the race (6-7 in total from different groups) and some of my much more talented friends ( 4 of them) did say they also found it more difficult than expected and their times had suffered.Though they were saying by 3-10 minutes not 25 like me. They mentioned wind and humidity as reasons why they thought their times weren't as expected. Be interesting to hear what others think.
But I'm sure a lot of people still got PB's in the race.
Solecrusher I echo pretty much everything you've said. I had a nasty asthma attack just after 20km, which was pretty horrible. I didn't know if I could get back to the start so after about 7 mins started running slowly again and finished but was 25 minutes slower than what I should have been.
But I thought the marathon was really well organised and the level of support around the course was fantastic.
We also stayed in a airbnb apartment about 20 mins from the start close to Vondpark. It was lovely and made it feel like were experiencing real Amsterdam.