It's alright to have a ton of 180's, just place them well. A 180 coming on to or coming off of the straightaway generally isn't good.
Give plenty of run up to some of the bigger jumps and make sure all the jumps are built well. Test the jumps with several cars before completing the track and make sure they're all straight and easy to jump. You'll be able to tell if the faces of the jumps aren't right.
Watch for blind spots.