How often does UA switch one configuration of 777-200 for another? I am booked on TLV-EWR in J. The seat map shows Version 2 (2-2-2 in J). How likely is it that I could end up in a 2-4-2 configuration (and are the bad reports of that seat accurate)?
Odds are close to zero for that particular swap.
You might see a swap to a 772 with Polaris seats, which would be an upgrade.
And yes, 2-4-2 is not good (though the seat itself is very comfortable, if very narrow).