As far as your reduced frame rate goes, I would say give it a few more days. I know last night (10/25/12) RIOT had a bunch of Champions unavailable because they were broken. During this time, I played a game on the new map where one of my opponents was Akali. Every time she dropped her Twilight Shroud, My Computer would freak out. I had frame rates jumping all over the place, I experienced server lag, and even some spell effects weren't working right. (I think Trynd was trying to use spinning slash, but you can't imagine how freaked I was when Tryndamere threw another Tryndamere at me!) I have had similar experiences in other matches on that map, but none quite as bad as this one instance.
At the moment, I am fairly convinced that the droves of people complaining about lag aren't just looking for an excuse for dying in the given situation. Furthermore, I don't think they all are accustomed to running the game on minimum settings. I have played the new map on several different machines, and even my lowly laptop can maintain ~30fps in most teamfight situations. However, every one of my computers has run into some sort of issue at some point trying to deal with the new map. I don't know that it is the case for all of these situations, but I am blaming the bugs.