I enrolled for TSA Pre today at LAX Terminal 5. I just walked in the office after getting off my Delta flight this morning, and there was no wait. The whole interview and fingerprinting process took less than 15 minutes.
Best part is, the contractor who processed my application says that most of the Precheck applications come back with a KTN# in 3 business days or less, not the 21 days the web site and receipt advise. We will see if that actually happens.
CMH, if you're flying to an airport with a PreCheck enrollment center in the terminal, you might want to try your luck and just walk in when you land. I can relate to your situation as my home airport (RIC) has a PreCheck line at the checkpoint but nowhere nearby to enroll.