I second hsumh316 's opinon. First of all, Delta One lounge is not only amazing, it also has its own expedited security and bag check. That alone is worth it.

The new airside connector to Terminal B from Terminal 3 makes the trek to the AF lounge and departure gates easier.

NOTE: entrance to the D1 lounge and security is on the Arrivals deck–not Departures–at the end of T3.