And nor is HDR Motion blur, or the sprite-based DOF. And the improved tone mapping isn't, either.
I can't see what's so DX11-ish about the shadow update, and motion blur/shadows for particles. (Read DX11 up on Wikipedia.)
I've to agree there. They put DX10 and DX9 features as DX11 only when they aren't. People with DX10 cards will continue to see a blurry game knowing their cards can do those effects with their API level. I don't think adding DX10 paths for the same effects is hard to do when you have the DX11 part done.
It's always a waste of money.
A waste of money is when you spend money and you get nothing in return. Upgrading PC hardware improves your computer across all software you run on it. Upgrading graphics card improves Crysis 2 experience along with the rest of games and apps that can use your card, past and future apps.
It's up to you if you think it's worth it or you can get better value spending money on other components/things you use on your life.