Perfect Day is about a day that is not so perfect (although the story is about as close to perfection as you can get). I think others have covered all the great points pretty well so I thought I would fill in a few background details that non-Oregonians might not be aware of :D
1. OMSI stands for the Oregon Museum of Science and Industry. It has a laser light show in the Planetarium (I think, it's been a while since I've gone). It's a GREAT way for people of Wyatt and Graham's education to meet and mix, people of all orientations and genders.
2. Bikes vs cars. Last year there were a series of horrific bike accidents, where car drivers who were either careless or outright murderous killed several bike riders, including one incident where a driver pulled in front of a group of bikers and deliberately braked suddenly on the downhill, causing serious injury and death. In other cases there were several hit and runs, like the one that killed Jase. The amount of sheer hate directed toward bicyclists was shocking, victim blaming at it's finest.
This is a very enjoyable story and I hope that a few people find these details helpful :D