I love Boulder. Moved here 7 years ago.
Yeah, the wind is annoying sometimes. Yeah the trails are crowded (people like me moving here in the past 10 years have added a ton to that!). My biggest "complaint" is that it is hard to access tracks for a track workout (at least during a school day)....plus the (outdoor) tracks do get covered in snow/ice quite often!
I ran for 5 winters in Ithaca and 3 winters in Michigan. The winters here are a piece of cake compared to that. The northeast and midwest have generally much harsher winters on average IMO.
And the summer running? It's really not that hot because there is very low humidity most of the time. Whoever said they had to "run before sunrise" in the summer here is totally full of it.
I agree the elevation is "too low" to be sleeping at. I'd rather be at 7,000'-8000 feet (and yes, i did live in Nederland for a summer). I often go up into the other parts of Colorado for high altitude trail running/ big mountain running...but I'd also say "altitude is overrated in general" too.
To really like Boulder (or any place) I think one has to like the town for aspects outside of running. I like the food here, I like the beer here, I like the bike path network and the coffee shops and the music/art. I like the political landscape. I like the view of the flatirons and the fact that the sun is so bright I have to wear sunglasses most days. Real estate is definitely overpriced now and there have been some changes that I'm not fond of (even in my short time here), but overall it is the best place I've ever lived in in the US.