You might find more info in the Trusted Travelers forum.
I've had GE for about six years, and it's a big time-saver. If I come back to SEA with hand baggage only, the shortest time between aircraft door opening and opening the door of my flat has been 30 minutes, and I live about 12 miles from the airport. Checked baggage slows it down. You get Pre-check as part of GE, but not for BA flights (unless its randomly assigned, which TSA are reportedly cutting back on).