1. Exports are more tricky... If you export a table that is protected under OLS and you want to import to another database, then that database schema must also have OLS installed with label column defined
2. When you create a new user in the database you must consider the label privileges for every new user.
3. Your algorithm for implementing OLS against your business needs some times takes **a lot** of thought (like it did for me). I needed triggers on many OLS protected tables for my business algorithm.
Don't blame me, I'm from Red Sox Nation.