I created a different way of midtone sharpening actions that can be downloaded here.

Here is a list of what each action in the attached file does:

Midtone Sharpen 16 LAB

This action works on a 16-bit per channel file. It converts the image to LAB color and creates a mask to use with the USM filter. Since the mask has to be 8-bit, the image is temporarily converted to 8-bit mode, and the mask is created and pasted into a new file. Then the original image is reverted back to its' 16-bit state. A selection is applied to the 16-bit image, using the
8-bit mask file as a guide, and then the USM filter is invoked. The way the mask is created, it focuses the USM filter on the midtones of the image, and keeps it away from the shadows and highlights. This means that the USM filter can be applied much more aggressively without causing halos or sharpening image noise in shadow areas of the image, resulting in much more micro-detail in the image without objectionable sharpening artifacts. This action does have one significant quirk; before running it, close all images except the one you intend to sharpen, and tile your document windows. Otherwise, after creating the temporary mask document, Photoshop may not switch back to the correct image document, and the action will halt with an error. If anyone has any advice to overcome this, I would be very interested in hearing it. Useful settings for the USM filter in this action are 100-300%, radius 1-3, threshold 0, depending on the image being sharpened.

Midtone Sharpen 16 LAB A & B

These actions together are the same as the plain midtone sharpen LAB 16, A ends right after the temporary mask document is created, and B picks up where A leaves off. This is useful when sharpening portraits, where you may not really want to sharpen the subject's face. Simply airbrush the mask black where you don't want to sharpen, then run action B.

Midtone Sharpen All 8 RGB

This action is intended for multi-layer 8-bit RGB files. It makes a new layer called Midtone Sharpen that is a merge of all currently visible layers. This layer is moved to the top, and its' blending options are set so that it is 51% opaque in the midtones, and transparent in the highlights and shadows. USM is applied to this new layer, and the blending options focus the sharpening effect on the midtones of the image. There are no quirks with this action, you can use it with as many open documents as your computer can handle. Useful settings for the USM filter in this action are 100-300%, radius 1-3, threshold 0, depending on the image being sharpened.

Midtone Sharpen Current 8 RGB

This action is the same as the previous one, except that only the current layer is duplicated and sharpened.

I hope you find these useful, I use these actions on all of my photos now.