I just got back from a business trip to Denver. I thought I'd give my prospective on the city from the point of view of a Portlander who usually only uses bike and transit to get around.
The transit was pretty solid, at least for downtown and inner suburbs. I took a light rail train straight from the airport to downtown. I had the option to jump on their Mall Bus (will get to that later), but I decided to walk instead. My only complaint was that the ticket felt a bit steep at $10.50 when traveling from the airport. I'm used to a $2.50 flat fare, which both encourages use of transit and is far less confusing for a traveler new to the area.
The Mile High City has a mile long downtown mall that is exclusively pedestrian, bicycle, scooter, and the mall bus. The mall bus is frequent and free. Retail of various types lines the mall, both chains and local retail. To show the contrast between your typical North American stores, there was a Taco Bell that took up maybe 800 sq ft (74 sq meters) at most and was rapidly serving customers. That contrasts with a Taco Bell in Portland that gets similar traffic, but is spread over 25,000 sq ft when the building, landscaping, and parking lot are included.
Now, my two "fuck cars" moments. They have ridiculously overbuilt their roads. Downtown has four lane roads through it. Seven lane stroads (three lanes each way plus turning) are common. These dwarf Portland's roads, even though Portland's metro population is almost identical.
The second was when I was doing a little traveling around the area. Density drops off considerably when you exit the urban core. There doesn't seem to be any effort to keep the city constrained from sprawl. Go out just a few miles and you hit the soulless suburbs with little apparent effort at urban design or infill.