I don't know if we have just gotten used to the crowds but we don't think they are really too bad. You can definitely navigate through the parks.
The most popular attractions like Space Mountain, Mission Space, Soarin', Dinosaur, etc. will have waits of up to 120 minutes in the afternoon.
Just make use of Fastpass whenever you can and you'll be fine.
We take the Magic Kingdom in two days. We concentrate on one side of the park on one day and the other side of the park on the second day. But, then again, we want to see and do EVERYTHING in the park. If you were up to skipping many things like Hall of Presidents, the Riverboat, Tea Cups, etc., you could definitely see the park in one day.
We also take two days at Epcot. We like to really explore the Innoventions buildings and the countries and we know with two days, we can take our time. I think Epcot could be done in one day too.
Our visits to Hollywood Studios and Animal Kingdom are one day each.
Just get up early and be at the parks at opening time or slightly thereafter. Don't take the time to eat breakfast in the parks. Just pick something up at your resort and eat it in your room while you are getting ready.
Hit the big "must sees" on your list first thing in the morning and utilize Fastpass for the others you don't think you'll be able to do in the a.m. or early afternoon hours. Just keep in mind that the Fastpass for some of the most popular attractions are sometimes gone by mid-afternoon. I have seen the Fastpasses for Winnie the Pooh all distributed by 1:30 p.m. No more for the rest of the day.
Just let me know if you have more questions.