"...PetSmart... if I miss American amenities.

If I may chime in, as much as I would like to do some Expedition-type travel, explore Baja, perhaps bring toys and food during Christmas, etc., I was put off as well during my last visit across the border.
Just like what Phil has mentioned about crossing the border just to enjoy some local delicacies, I remember when me and my coworkers would go to a favorite place in Tijuana just to enjoy some good ole fish tacos while watching the busy streets eating with the locals... then going to work right after.
My last trip was one Memorial Day a few years ago. We were a less than a mile away from the San Ysidro border on our way back to San Diego when we were re-directed to Tecate due to traffic. Not being familiar with the area, we were circling around for hours trying to find the entrance to the US in Otay. In process, we managed to get ourselves pulled over by a local cop. Apparently, while in the busy freeway on an Xterra with a 16-foot kayak strapped in the roof rack, we were actually "speeding" and was told that we would have to follow the local law enforcement to the precinct that is an hour and a half away. Annoyed and frustrated, I pulled my last $20 and was so glad that it was good enough to settle our speeding infraction.
From there, it was a 5-hour long wait to cross the border back to the US... literally inching our way.

And then there was this one time in Rosarito...

Never again.