Chris from MustangTuning.com called me this afternoon and was extremely kind and apologetic about what took place.
He offered to take the tires back, even though he didn't have to, and I appreciate that immensely.
However, I did not take him up on that, mainly since I gave the tires to the guy who aqcuired and installed the Nittos for me.
He was so friggin careful and took probably an hour longer to do the work than he quoted, so I didn't mind.
I already have a stack of oem wheels in my shed higher than my head lol, so I didn't need more rubber hanging around anyway.
Nevertheless, Mustang Tuning.com gave me a 10% refund and I got an email confirmation that they sent out new lug nuts.
After talking with Chris (the MT.com owner) I am convinced that they will take steps to keep this from happening in the future, so I accept his apology completely, and I'm satisfied with the results.
As I said before- they ARE impressive wheels, and I'm glad to have them.
So now I apologize to Chris for the tone of the first post in this thread, though I am still very glad this forum is here to support me and you when something like this happens.
I have contacted the Webmaster and requested that the title of this thread be changed to "UPDATED: MustangTuning.com resolves issue"