JAL charges $300 USD to upgrade to PE at check-in provided seats are available.

I haven't flown it so can't speak to whether it is worth it or not.

If traveling in pure Y, JAL is probably the best with NH a close second (most NH planes are good but a few have been refurbed to have tight Y) whereas JAL has 34' in Y (many don't even think PE is worth it because Y is good enough).

DL "PE" is not PE at all. It's extra legroom and a free drink (similar to Economy Plus or MCE on UA/AA but with the extra food/drink which isn't particularly relevant on a TPAC). It will likely be much cheaper than NH/JL PE for that reason.

Here is a JAL PE review: http://www.flyertalk.com/forum/japan...my-review.html