We don't get to see resumes until after HR has screened them for buzzword compliance. Prior to the absolute hiring freeze, we didn't see too many programmers with a degree at all.
With that said, for the mid-level developpers I have personally been involved in interviewing, I find it to be a positive mark but hardly decisive. I have personally always given an interview to someone with a master's degree on their resume.
Of course, more than one of those people with masters did poorly in the interview, while I have also seen people with no degree at all do very well.
So in short, I think that a master's will normally help you get an interview, but rarely play much of a role in actually getting the job.
It's part of an elite.