The USCIS received my answer to the RFE on I-140 (mine was EB2-NIW) on Jan 12, 2010. They approved my I-140 the following week (actually Jan 20, 2010). Not only that, after 2.5 hours of approval of I-140, they approved my (along with my family member's) I-485 also. It was a surprise to me.