Form what I've read and seen so far upgrading from a D30 to a D60 doesn't seem particularly worth while. The AF is a little improved for low light, but I doubt this is a key factor for most of us. The 6mp CMOS is clearly a desirable feature, but unless you need VERY large prints (A3 +) then the D30 output upsizes remarkably well.
Personally, I'm trading up simply because I bought my D30 on the condition that if Canon released a replacement within 30 days, I could swap it for the new model ... seems silly not to
Colin K. Work, Pixstel