Like I said, I've only read the first one, but while some deaths disappointed me, they did seem necessary to progress the story. I know some of the other characters who die in future books (got curious and looked ahead), but I suspect that in each instance, it's less to just be a "shock" killing and more to advance the story.
Basically, though, I wouldn't trust Martin to keep anyone wholly "good" or "evil" (well, most of the time), and wouldn't trust anyone to say on one side or another, or to live or die. There aren't any guarantees, but it's not like watching a Joss Whedon show -- "Oh, look. Someone in love. $10 says they're dead in the next 5 episodes."