Opening day was our only trip to CT last year. We got there right before opening hour. Crowded, crowded, crowded. 2+ hour waits for the penguins (so we skipped them), line for Santa crazy (so we skipped that too), the shows were packed except the outdoor Christmas tree light show which was about the only thing we saw besides walking around and riding the train, food concessions all had long lines (we did get a hot drink in Grogan's on the way out and that was all we were willing to queue for given the long lines), Festhaus packed, shops packed. Brewery smell really strong and we were cold and there just didn't seem to be any nook or cranny to just rest and warm up, though we did pause by the outdoor heaters to listen to a sadly mediocre group playing outside in New France. I'm sure the crowd negatively colored our impressions of CT but we didn't see enough to make it worth going back to as a separate ticket event. So I'm definitely with robbie on avoiding Christmas events on Black Friday as I might have been more impressed if all the main attractions hadn't been so crowded.
I also naively thought they'd have some kind of "grand opening" moment with some kind of special welcome to the first Christmas Town in history (just like an announcement or something), and I in a silly way thought it would be special to be there at the opening moment of the very first CT but obviously that turned out to be a dumb notion on my part and we heartily wished we hadn't blown our tickets on that day.
Of course you can't predict that that will happen again this year but we really, really disliked our CT experience. Riding the train and just looking at the lights was about it for us and it sure didn't make us say, "Now THIS is Christmas." Given my experience, I'd only go opening day again if I knew I would have plenty of other chances to go.
ETA: I really don't think the overall number of people was excessive it was just that the crowd really bottled up around the attractions and shops. You could barely wade through in places but walking from area to area was generally pretty quiet. So it was more an issue of long queues for attractions, food, and shops than an overall crowd issue, which I have certainly also experienced at BGW.