Some findings in the last two weeks of this:
Journey times are largely unaffected (less than 10 miles each way to work).
Fuel economy has only risen very slightly.
It's more relaxing with rising levels of smugness

The brake pedal is largely redundant.
The car stays clean.
Other cars joining A-roads from slip roads are a problem, I'm too slow to move over into the express lane for them to filter in and they're doing about the same speed as me.
I'm attracting the worlds worst tailgaters

Insignia drivers are horrid.