In my experience, don't let the crew dictate questions (eg: what was ur original seat, who are you flying with, what's your name etc..) I appreciate not everyone is as confident, but if you can take control of the situation fast, and overburden them with information you will put their mind at ease about your being there "My partner was allocated this seat, and he kindly gave it to me for extra brownie points, he is in 44E and his name is Mr Gold. I trust this seat swap is okay with your crew."

Crew see 'self-upgraders' on almost every flight and quite rightly, these people are promptly sent back. This is where the perceived negative attitude of the crew might come from.

Interestingly, I experienced the flip side of this on the weekend. On a non-CX flight (where I had no status), the pax next to me changed seats before takeoff, without speaking to the crew, as they didn't want to be next to Little Miss Doot (and with plenty of empty seats further back - it's perfectly understandable). I proceeded to move over one and take their original seat. The manager came to greet me after takeoff, offered me wine, anything I needed, etc. By not telling the crew - I assumed my old-seatmates in-flight status benefits :-) This is why you should always alert the crew prior to moving.