My family uses sunblock when we're at WDW mainly because we don't want to risk a major sunburn ruining our vacation. May not be the best reason, but it works for us.
My DS10 and DS5 and I use sunscreen at home when we're going to be in the sun for any "considerable" amount of time - swimming, gardening, mowing, etc. However, my DH does NOT and he still get burned even with dark Italian skin. He also has a lot of moles that makes me paranoid, but he rarely uses sunscreen at home.
I also use a daily facial moisturizer that has spf in it. Have you seen those women that look 80 when they're 50 - that isn't for me!!!
I just love the sunscreens from Arbonne International (disclaimer - I am now an Arbonne consultant because I LOVE their products so much). Anyway, they aren't GREASY like so many others are. They seem to absorb into the skin more like a good moisturizer (not one that lays on the surface).
I also use Arbonne's self tanner - I hated even the thought of that before, but now I like taking care of my skin, but still having a nice natural looking tan.
I've also heard that an SPF higher than 30 isn't always a good thing. They have to add too many chemicals to get those incredibly high SPFs. My understanding is that the better option is to use 30 or lower and REAPPLY!!!
Anyway - great thread going here and it's nice that the flames aren't flying.