Well, I assumed Mulgrew's appearance wasn't considered a surprise or they wouldn't have listed her. You're certainly welcome to hate what they did in First Contact and Voyager, but that still does change their intent with Picardo's cameo. Honestly, while Voyager isn't my favorite series, I still enjoyed the EMH's unexpected experience and it seemed to get a great reaction in the audience I saw it with.
Actually, that's how I saw it too. People generally LIKED Picardo's character... and Russ's character... most of the rest were just sort of "casual interest" characters, but the two leads were pretty much disliked by most people I know.
As for why Jeri Ryan turned it down... I'd never heard that bit, but if true, it does fit. That's about the same time that her husband was being forced out of the Senate race through the illegal revelation of his and Jeri's divorce records (clearing the way for Obama to "sweep in and save the day"). I was a big fan of Jack Ryan and planned to vote for the guy... and honestly, the fact that the guy had a few "kinks" to share with HIS WIFE was hardly something that I'd have considered a reason not to vote for him!