I avoid using it for that reason. I don't agree with Specter or Snowe much of the time, but they are Republicans. Not Conservative, of course -- but still Republican.
I reserve RINO for a politician who says he's a Republican but votes with the 'Rats more often than not. Two examples are Jumping Jim Jeffords (before he jumped) and Senator Lowell Weicker.
You'll get not disagreement from me .