Mean Mommy?

You know those days when your kid is acting horribly, and you've exhausted your usual repertoire of disciplinary actions, and child is still terrible, and you have to resort to something you've threatened but never actually carried out? While your actions as the parent may have the desired effect (i.e. obedient, tame child), you're left wondering if you're a horribly mean parent for having carried out the punishment, or if you're horribly ineffective as a parent because you had to resort to this measure and because you have a terribly misbehaving child, or if you've bitten more than you can chew because you decided to have children, or if you even deserve to have children at all? Come on, we've all been there! If you haven't, I don't want to talk to you anymore!
So last night, Devlin was acting up. In fact, the misbehavin' started from the moment he woke up in the morning. There's a children's book titled "Alexander's terrible, no good day". Well, we could have written one that was entitled "January 5 - Devlin's terrible, horrible, no good day".
He said he received a time-out at school but was unable to tell me why. Our nanny reported he didn't nap in the afternoon. He was whiny during dinner, although he ate without complaint. He dawdled getting ready for gymnastics. He yelled when asked to get ready a bit more quickly. He ended up on the naughty stool for a time out and screamed the entire time. He even threw himself on the floor. We debated on skipping gymnastics given his behaviour. In hindsight, we should have, but gymnastics tires them out, and the classes aren't all that cheap. So, off we went. His listening skills were horrible, and he ended up missing out on the trampoline because of his misbehaving. He even refused to leave the gym and Daddy had to physically carry him out. Daddy felt he deserved a good spanking or some significant time on the naughty stool - which had already proven to be ineffective earlier.
On the drive home, he was asked what his punishment should be for his actions. He replied, "Take me back to the hospital."
A bit of background - I was once threatened to take him back to the hospital where he was born because I was sure there was a switch-up at the hospital. I told him there was no way I could have given birth to such a misbehaving unruly child. I told him I'd return him, and find my new baby and he could look for his real parents. It's kind of like the threat where my parents told me they'd leave me under the bridge from whence they found me.
Well, I was tired, and fed up with his mouthiness, so I dropped off Ceilidh and Daddy at the house, and drove to the hospital. There was some whimpering from the back row, but no protest. We made it all the way into the parking lot of the emergency room before Devlin begged me to take him home, all the while promising to be a better listener. We had a discussion about his talking back, his attitude, and his tantrums. He even provided some insight into his bad actions - he said he didn't take a nap and he was tired. I drove back home.
So, am I a horribly mean mother who probably broke all the rules of discipline as set out in Supernanny, Nanny 911, Be a Better Parent, Dr. Spock's Child Rearing and Discipline, Raising Happy and Healthy Children? Or am I your average mommy who's tired, over worked, desperate, and sometimes has to resort to creative or wacky methods of discipline. (Same ones that were used on her as a child, and I turned out okay, didn't I?)