Oktoberfest actually starts in mid-September, as the weather is nicer. I went to the opening in Munich, and discovered that this is not the event for me. In the morning was the opening parade, when all the marching bands escorted the horse drawn wagons of beer casks into the festival grounds. It was fun to see everyone dressed up in their traditional gear, both in the parade and especially the spectators (I had no idea that so many people would dress up), and the parade was great, but later the crowds were really overwhelming even outside the main tents and the smells and garbage and drunk people and carnival rides/ flashing lights all combined to be an almost of nauseating sensory overload.
Neues Rathaus, Marienplatz
I am far happier with the beer halls, which were much more civilized (mostly just allowed for more personal space).