OK, I'm probably going to be very inarticulate, Giles, but I'll give it a go.
I look to my mum. She is a staunch Catholic, but is perfectly capable of forming her own judgements about what the church is up to (she wasn't too keen on Pope Benedict) - I think for her, her religion is quite a private thing, she certainly never talks of her beliefs.
She also knows a lot about other religions, especially Judaism (the synagogue is at the bottom of our road and the rabbi lives on our road) and Hinduism - for example, she will usually know where in their religious year they are, and what each main festival means. We were talking about eruvs the other day and she was able to tell us a lot about them and how they work - she didn't agree with the idea but at least she had the information!
She is interested, informed and non-judgemental. Her beliefs clearly mean a lot to her (the church was very supportive when my dad (not RC) died, and in fact his ashes were the first to go into her church's remembrance garden, even though he never attended mass there) but she's not insular or narrow-minded (we didn't attend an RC school, for example, though we did have to go to mass every week).
I also think it's impossible to understand the history of many countries, including our own, without knowing a lot about that country's religions.
Although religion means so little to many of us in the UK, globally it means a lot to a lot of people. And I think the more information we have, the more we can try to understand about many of the conflicts around the world.
I find the questions hard too as I'm really not sure what my own beliefs are - DD is christened but we don't go to church and I feel so ambivalent about it.
See, I said it was inarticulate. Doesn't really make sense to me. I just feel very strongly that I want DD to know about certainly all the main religions of the world, and if that meant visiting a mosque a couple of times, great.