While there are a very few who will sit in the back of the theater and swear the screen is still too big, the majority sit in the center of the theater and they don't swing their head around when viewing, they just sit there.
In a typical movie theater, the screen is .66x the viewing distance in with. In more simple terms, a 12' viewing distance will have a screen size that is 8' wide, or a 110" diagonal! Think about that for a minute. That's to recreate a 'true' home theater experience. At 8' you would actually want a screen that is 64" wide, which is over a 70" diagonal for that same impact. So, while going smaller is a personal opinion, which you are free to have, choose, and decide upon, it is a simple fact that 65" is already small by THX guidelines.
It is also fact that the number one complaint people have after buying a HDTV is that they wish they had purchased the next larger size.
I very recently told a family that they should move their 50" flat panel to their bedroom and install their 70" flat panel in the family room and put a 120" front projection screen in the basement.
The wife was like "Won't that be to big?" - I promised her that she would be used to it in a shockingly short period of time.
I installed the 70" TV in the morning, and before I left the house that evening, she took me aside to specifically let me know that she was already used to the size and was very glad I had strongly suggested the 70" in the family room.
It just is established that for most people, they will get used to what is in front of them, and for the detail that HDTV offers, starting with THX recommendations and the viewing distance chart is a great baseline. From there, if you go smaller, and then wish you went larger, you really do only have yourself to blame at this point.