The seat swap thing has been covered on FT innumerable times. IMO, there area couple of rules to asking for a swap:

1) if the seat you are asking for is better than yours, DO NOT DO IT!!! If you are swapping for "same" or for "worse", then OK

2) When you ask, you make it VERY CLEAR that you realize it is a favor and that you will hold no grudge or ill feeling if the other party says no. AND YOU HAVE TO MEAN IT!

If you can satisfy those two conditions, ask away. If not, keep quiet.