Since no one has chimed in with any alternatives to PhotoKit Sharpener 2 I thought I'd share my two cents. I use Nik Sharpener Pro 3
and couldn't be any more satisfied with the results. It's that rare combination of software that is easy to use but incredibly powerful. I use it for all my sharpening needs whether they be for jpegs on the web, canvas prints, fine art paper prints, etc. I've never used PK Sharpener so I can't compare the two. I can say, without a doubt, that Nik Sharpener Pro 3 is far superior to LR 3's sharpening tools.
Hope this is helpful. Let me know if I can answer any questions for you.