Shafroth is a nice guy who's been looking to run for office for a long time--he has no deeply held convictions that anyone can see, and if he's elected, he'll be a decent enough Member who will likely go on to lead the Caucus of the Obscure, and not achieve anything remotely worth remembering.
Fitz-Gerald is your traditional main-line establishment politician. She's a state senator from Jefferson County, and she runs the Senate with an iron fist. Essentially, the folks that gave us 12 years of Democratic ineptitude are the folks who are backing her. If you love John and Ken Salazar, and you hunger for the kind of bold, visionary leadership that they provide, you'll simply adore Fitz-Gerald.
Mark Udall has to love the latter quote, given that both John and Ken Salazar are trying to help him appear more moderate. It's a lost cause, but it is fun to watch Democrats try to out liberal each other.