Black Ops II will be supporting DirectX 11 on PC, meaning you'll get some more advanced graphics over what the aging DirectX 9 API can offer, and likely better performance to boot.
Graphics on all platforms, it's said, will benefit from a significant boost over their predecessor for once, thanks in part to effects like HDR lighting, bounce lighting, self-shadowing, and "reveal mapping".
As for other PC features, those aren't finalized yet. Dedicated servers, LAN, and the like, all seem to be possibilities under consideration at this point.
The game was officially unveiled last night during the NBA playoffs. Check the debut trailer here, if you missed it.