OK, here is the promised data:

The average speed for the 9mi ride on flat for three days preceding new bike on the old 33lb. mtb:
18.0, 18.1, 18.3 mph

The average speed for same ride for three days on new Poprad:
18.1, 17.6, 18.0 mph

It feels so much smoother to ride this new bike with road tires. But I really knew the mtb well and because of this felt comfortable pushing very hard, etc. I still need to get used to new bike before being able to focus on pushing as hard instead of getting used to new handling (which is better) and controls.

Al