Fairly easy to navigate, especially because traffic at Terminal 3 is much lighter than the frenzied Terminal 1. And I'm talking about passenger and vehicle traffic being much lighter. Departing flight passenger drop-off is easy with curbside service and there is plenty of curb room to maneuver. I hate dropping people off curbside at Terminal 1 because it's like a feeding frenzy and game of chicken with the taxis, but no such stress at Terminal 3.
On our recent visit, we had a good experience with a parking attendant, who was helpful when we left our ticket at the machine after paying. In addition, the security person (a woman from Hawaii) was so friendly and informative when we were trying to figure out the parking levels and where our guests would be walking out. Note to self--the bottom level is zero and the elevation one would think is the second floor is referred to as Level One.
On past visits as passengers, we disliked the long walks and long waits at security. But after the newness wore off, it seems TSA got their act together and the lines moved better. Friends and family who were accustomed to the little, intimate Terminal 2 still complain about the long trek from arrival to carousel to parking, but it's the way of the world now.
Plenty of short-term and long-term parking, no matter what the season or timing is.