The ACR sharpening IS the PK Sharpener that you've used in the past...
Actually no...the capture sharpening in Camera Raw and Lightroom is designed with the CONCEPT of PhotoKit Sharpener's capture sharpening but it's not directly based on it. The output sharpening in Lightroom (and Camera Raw) is however directly based on (and improved on by Eric Chan) PKS output sharpening...
Sadly, Bruce Fraser had passed away before he got to work with Thomas Knoll consulting on the improved sharpening in ACR 4.1. However, I followed up and worked in his place to substantially improve the old sharpening.
The big difference is I think ACR is a better place to do capture sharpening (and noise reduction) than later in Photoshop. Note, Neither ACR nor Lightroom have really good creative sharpening (which I still do in Photoshop with PKS).
PixelGenius is working on PhotoKit Sharpener 2.0. More info on that when it's available...