I was there today when the show just opened. Both M3 and M4 were locked, but no other cars were locked except the i8 was behind glass. I asked a salesman on duty there if I could see the under the hood, he went to the counter to ask for the key, but came back that he is not allowed to open them, and suggested I should go ask the "boss" behind the counter.
I asked the boss man if I could see under the hood, but the guy replied rudely that they are locked. Duh! He then said they don't have the keys. I said really?! He went on to say they were locked for press and media during the press event. He just blew me off. I guess to him I didn't look like I could afford one of these M cars.
I left to see other cars at the show. I came back later and saw a different salesman in the process of opening up the M4 to let a teenager in! This salesman was kind enough to let me sit in the car for 30 seconds. I didn't really have a good feel of the inside. It looked and felt nice. When I got out, he promptly locked the car up.
Both cars look very nice from the outside even though neither of them have CF roof. As others have pointed out earlier, the M4 rear wheel gap is taller than the M3's. And the M4's front wheel gap is also slightly taller than the M3's.
The "black" wheels are actually nicer when seen in person. It is very hard to gauge how they really look with the artificial lighting at the show. I am sure they look different (probably much nicer) outdoor.
There has been so much anticipation for me. So much so that when I finally saw the cars, it was kind of anti-climatic for me :-). They were just sitting there quietly, doing nothing, and locked. I guess the next thing is to hear and see the cars in motion.
Enjoy the pictures.