I have used one portrait software program in the past with CS4-5. It was "Imagenomic Portraiture". I quit using portraiture software a little over a year ago. I would strongly suggest you learn how to use the native functionality within PS CS5. You have all the tools to make any modifications you want within CS5. Unfortunately people want the easy out. You can tell in their images they want the easy out.

When people get the software they make several mistakes.

1) They overcook the image.
2) They do not correct underlying problems with the image before apply the portraiture actions.
3) They don't know what to correct before they apply softening.
4) They don't know how to modify(slightly) The light in a portrait.
5) They have no idea about how to change the tone via color.
6) THey have no idea how to create contrast via color.
7) THey have no clue about color and luminance whatsoever.

For many of these on this list the Portrait software will not help you. That's the rub. I would say that it depends on what level you want your photos to be at and how much effort you want to put in to get there.
I would say that most would help their photography and excellence more by going over to 500px.com and looking at the editors choice section. The popular section is also very good. You will quickly realize that you have not arrived and know very little. Looking at lots of quality images and how they're lit will improve your images dramatically provided that you practice shooting and spend an equal amount of time trying to emulate the post processing techniques of these images.

The question you have to ask yourself is:

How good to you want to be?