I agree with Maya about the inconsistency in sizing. It really depends on the item. Because of that, I rarely order anything from final sale unless I've tried it on in the store before, or it's an accessory. But the 20% off coupon this weekend is for any merchandise purchase above $175.00. In which case, the regularly price items would still be returnable, but any sale items would still be final sale.
I got another silk Elizabeth halter in the ivory color, which was already on sale and there was an additional 20% off sale items (in-store promotion), so it came to $25.00. That was my big J. Crew purchase for the weekend.