I'm a daily commuter (inbound only) on the I-66 HOT lanes inside the Beltway, and, wow, it's like night and day. It's a consistent 50-55 mph all the way past the Rosslyn tunnel. Motorcycles do not need an E-ZPass to use 66 during rush hour.
http://www.66expresslanes.org/using_the ... efault.asp
Removing the exemptions for "clean fuel" vehicles, "airport users" (which was largely unenforceable), and scaring off the cheaters with exorbitant tolls and fees seems to be working. VDOT's target is to adjust pricing to keep the road flowing at 45+ mph.
I do expect traffic to pick up once people adjust to the new set-up. For whatever reason, slugging never caught on in the 66 corridor. Maybe it will now.