Apps take forever to start on OS X Mavericks
When I see things like this I often suspect disk problems. (This is a HDD, correct?) The first symptoms of soft disk errors are often bad performance.

Open the Console and see if you see any disk errors. Also try booting into a Super Duper clone. Since a clone will have the same files, any problem would continue if it were a configuration problem. But if the problem goes away, it was likely a problem with the physical drive. As a bonus, a clone is exactly what you will need if you have a physical drive problem.