As a spectator, I just want to see final after final after final. I don't want to pay $150 for a ticket and $200 a night for a hotel (and that is on the low side) to see 2 track finals, some prelims and field events. And usually you can't pick a couple of prime days to see your favorite events. If you're into the 1500, the men's and women's will be in separate weeks. They just screw you over so every day is kinda worth seeing live, but not really.
If you need to have the prelims in Eugene, have them all the first week at reduced ticket prices. But the finals of everything should be the last weekend: Friday, Saturday, Sunday. Maybe the 10,000m need to take place somewhere else if people are used to doubling. Maybe you just need to see who can make it spaced out with just one day of rest.