Having the day off I decided to try the route. With the ride to work having the big uphill pull it took 1-1/2 hours. Turning around and coming back took 2 hours although in all fairness if this were a bike to work day, I'd have 9 hours of desk rest in between the trips.
So I can do it, and faster than the RTD says the light rail can (1 hr, 40 min) although by now I'm pretty sure RTD's number is wrong. Whatever. I'll stick with the motorcycle in the summer and the car when I have to in the winter (30 minutes each way).
FWIW the trip involves dropping down to the river, then climbing up the other side. Home to work, that's 239 ft down followed by 597 ft up with each leg being about 9 miles long. Or as Jeff the Cyclist says, such a trifling ride as not to be worth putting on the spandex for.