When my brother died, people would say that a lot to me. It's extremely common in my culture (Mormonism) and I even believe it, but that's something that you need to say to yourself, and not have others say to you. When other people say it to you, it's like someone punched you in the face with what you should believe, and it's not comforting, nor does it feel good in any respect.
However, if you really believe it in your heart of hearts, then shouldn't it be comforting? Similar to 'they're in a better place now' -- it seems like if both people believe it's true, then it should be comforting to talk about.
Maybe I'm a more "thinking" guy than other religious types, but for me, religion is about understanding who I am now, how to deal with life now, how to treat people better now, etc. It's not about some mysterious heaven / hell thing that scares you into being a good person. Religion for me is separated from mythology, though they do play into each other. (IE the nuts and bolts of how a religion comes into being are important, but the teachings and purpose of said religion are much more important.)
Given that perspective, with a catastrophic event, "now" will always suck, without exception. You have to work through now in various ways. The new reality is what you need help with, not perceiving the person in some sort of blissful future state.
That's why things like "I love you", etc., play so much better for me. I need a shoulder to cry on when I dream about my brother as if he's still fine and was hiding. I need people to help support me through hard times, not people to deflect reality and pretend like it's all going to be ok.
</rant>
Think about this, even as a theist you feel the need to ask yourself, why did your mother/brother/child had to die while others are still living, an irrational question by all means, that begets dumb answers; but it's part of a healthy mourning process and does help you get over it (IMHO).
I also don't think it's about religious people versus the others, as people say dumb things regardless of their beliefs.
I think this is a time in which it pays off to be religious. For instance, I do fall into agnosticism and question my religion quite frequently, but I just can't be an atheist simply because I cannot accept that the people I love (including my child for whom I'm capable to give my life if needed) will one day go into non-existence, sometimes painfully. That's an idea I just can't live with.
Choose your source...some one argue one is more accurate than the other:
http://en.wikipedia.org/wiki/Job_%28biblical_figure%29 http://www.biblegateway.com/passage/?search=Job+1&versio...
The true faith, does not seek reward for good behavior, nor bothers trying to understand the divine will, it simply accepts the Yoke of the heavens. in the case of Job.
He does not ponder the reason, it is all the same to him "...the Lord gave, and the Lord hath taken away..."
If there is a God, this is a compelling example of the value he places on human life.
If you're a Christian however, you do have a small comfort that death may only be the beginning. And that's really what Christians should hear - that the loved one is in a better place.
And yes I know, that sucks too as how could you really know that she's in a better place? But I experienced this myself and it sticks in the back of your subconscious, eventually giving you comfort.
It'd be a bit like getting a limb amputated. You know that it's going to be for your benefit, but while you're going through it, I doubt the comfort of "oh it's ok, at least your not dead!" doesn't exactly optimize your happiness. I'd wager if you're there for someone, showing your love and support, gossiping, etc., you'd likely do more good.