1. It asks a lot: Lutron will give you more than you can handle -- that's just how they operate. If you let it, it will take over your life. This is typically the reason people leave. I'm listing this as a con, but it can be avoided if you are intentional with your time and proactive about dealing with the most pressing issues.
2. Salary (based on responsibilities): Overall, Lutron under pays engineers compared to the market based on the breadth of skills required. They have been working on this in recent years but they're still middle of the pack. I'd argue that the people who stay at Lutron for 5+ years aren't in it primarily for the money (not necessarily a con).
3. Transparency: Lutron is private (and still mostly family-owned) for a reason. They value the ability to make decisions behind closed doors, so some policies and approaches are not transparent.