I guess I should have warned you that anytime you flash the phone's firmware, the first time it boots it's going to hang on the splash screen a long time while it rebuilds the file system.
Somethings you just assume everyone knows after you've been doing this a while.
I am so glad you got your phone working again. What you did is EXACTLY what the AT&T store would have done anyway. BTW, if you lost the loaner phone with your sim card in it, did you get a new sim or did the phone eventually turn up?