Hey, glad to see my thread is alive!
Stinkerbelle,
Yes, there is a slight difference with the shortening and the butter
First, of course, is the taste. I like real butter!!!
However, I am thinking that with the butter you will get a 'crisper' cookie, and with the shortening, you will get a slightly 'softer' cookie.
Since I like to bake with real butter. (yummy) I often use 1/2 butter and 1/2 shortening!