I was just in Denver - I originally had been planning to do the Super Shuttle, but I arrived really late (around 11pm) and the Super Shuttle people wanted me to wait another 20 mins for a van. As it turns out, the cabs have a flat rate to downtown, so it was $47 plus tip and it took only about 25 mins to get to my hotel (almost as long as it took for me to get from my gate to outside the terminal where you get cabs - jeez, is that a hike!). The extra $$ was worth the time I'd have spent being cranky and tired doing more waiting.