I may also be a pollyanna, lol, and I am not at all surprised by the negativism concerning downtown Eugene. I regularly go to the downtown area including after 10 pm--and on my bike--and I generally like the vibe even if the company is occasionally challenging. I find that the establishments in the downtown area have better and more interesting food choices and bars including frankly, a younger and more vibrant crowd than in downtown Springfield the denizens of which I assume are likely tucking themselves into bed around the time I arrive. The Fifth street area is also fun later at night as are establishments in the Whiteaker. 
https://www.youtube.com/watch?v=Iwcp87cN16U