If I'm just running errands on my bike and going to be on it for a few miles here, a few miles there, I won't bother with lubricant. But on any "actual rides" I use lube, even if it's just 10 miles. I do get chafed without it. I've used Chamois Butt'r (works just fine), Assos (ok, but I think it breaks down really fast if it's at all hot out), Body Glide (my standby), Astroglide (this didn't work at all for me, might as well have used water...)... I slather lube liberally all over my chamois, but not on my body (this is actually one of the reasons I like Bodyglide, it's much less messy to apply to the chamois than, say, Assos).
I think the lube question is like the saddle question or the shorts question -- ultimately it comes down to personal preference and the only way to find out is to try.

