Quote - "2. GR can produce very nice results with Skin renderings but you have be very careful in how it's used as it can produce too much color bleeding.  I've found that using the "Optimizing for Outdoor Rendering" switch and turning down the GR gain can help."

Color bleeding is one of the reasons why I use GR and not GI. This phenomenon happens naturally in real world but GI does not simulate it. Of course, I have to be careful on not overdoing it.
The other reasons for using GR is that it makes the skin warmer and does a better job (IMO) of faking SSS.

Quote - "3.  For me anyways, I normally use GI atmospheres for character renders since it's easier to produce better looking shadows and control the overall lighting."

Yes, but where's the fun in doing it the easy way? LOL :-)