Good information AlwaysUpThere. Sorry Lindsay Wilson I was a little misleading.
Superseats are NH Business product (not JAL), with airport upgrades available from any fare bucket at an additional 5,000yen O/W, or about $Aus60. With a SuperSeat, you get a bento box (delicious), slippers you can take and unlimited alcohol etc.
J-Class are the JL "Business" product, with upgrades only costing 1,000yen, or about Aus$13. For this you get a bigger seat, 1 beer (only) or coffee/ soft drink and some nuts. In Y you get juice.
The NH Superseat class is seperated from Y, with usually only 2 rows allocated. The JL J-Class is quite large.
As AlwaysUpThere mentioned, no access to lounges on these fares unless you are an elite. But the lounges are nothing anyway, except the wonderful beer machines described, which are available in both JAL or ANA lounges (The only other time I've seen a beer machine in Japan other than at an airport lounge is in FUK at an izakaya, per my TR).
Also when they check your baggage receipts, they remove them with your "priority" stickers.
Back to my musings. I was thinking about if you bought a cheap JL Y ticket (e.g. Chowari), and then spent only 1,000yen at the airport to "upgrade" to J-Class, I wonder what % it would accrue. If you bought a ticket this way, it would probably cost about 33% of a full Y fare, and open to abuse if indeed it earned more than a full Y (100%) :wink: .