Hi Alyssa - I live in Denver, but my parents live in Boulder and my sister lived there for years. Although Boulder can be called "hippie", it can also be called "yuppie"! There are lots of young families and it's quite pricey to actually live IN Boulder. But, that said, it's a beautiful town, set right against the foothills. The hiking, particularly at Chautauqua park, is amazing! There are lots of restaurants, a great farmer's market, lots of dogs, and DEFINITELY lots of outdoor activities - biking, hiking, rock climbing, running, you name it - it's there! And like someone else said, the University provides lots of culture and entertainment.
I really don't think it's that cold here in winter - but I moved here from Boston, so the lack of humidity makes a huge difference! Some days will be cold in the winter and you'll get a couple of feet of snow at a time, but it generally melts within 2-4 days and it'll be 60-70 degrees for a couple of days. I found last winter completely painless...though 06-07 winter was a different story.
Boulder is pretty liberal, so if you are conservative, I may not suggest Boulder for you. Colorado Springs, on the other hand, is also in the foothills (about an hour south of Denver), but tends to lean further right. It all depends on your political opinion! That said, Denver is hosting the DNC in August...