Does your credit card signature really matter? It appears not. Great read and very funny, if for nothing but the description of his own writing/drawing talent. Link from random($foo).
The only time I've ever heard of any problem with credit card signatures was when I was down in Yosemite many years ago and was on the phone and overheard the young guy on the phone next to me telling someone (parents? relative) how he had denied someone a purchase because he didn't belive the signature was legit. That's it. Sometimes I will jokingly ask "that close enough?" when I hand back the credit card slip, and generally get a "sure" or polite smile that one reserves for people who ride the short bus but who are on a field trip.