From my 2 bits...i find the CX staff on the 1st class counter in LAX horrible (never done the JFK sector) but if they are anything like the cx check in staff at lax i share your pain.....infact many times I've gone across to the business class counter just because i've always had bad impressions from the 1st class check in staff......

As the OP could have blocked the exit row in advance, or done what ever (even these days you can request (not guarentee) to block the seat next to via MPO and they send a request in....however regardless of any of the above, the courtesy and service response from the CK staff is horrible (especially in the US)....

On a brighter note I just got back from LHR last week and as checked in early and the 1st line was empty, my check in procedure was quick, swift and easy, yet the check in agent spent 15 mins chatting with me.....which was very pleasant and she had great customer service skills....(dont worry, I've had my share of bad experiences too at LHR but i'll save them for another forum...)

Bottom line, CX staff is luck of the draw, u sometimes get lucky, or you sometimes wish you never checked in !