As for switching seats, I'm always willing if they can give me the same kind (aisle, window, or whatever) that I have, especially in coach. But no, I won't trade my aisle exit row for your middle cramped row!

My strategy when I'm with somebody and can't get two seats together is to get two that would be together if they were in the same row, such as one aisle and one middle elsewhere. Then either of us can ask our seatmate to change, and we're offering the exact same seat they had. Never had a problem using this approach.