I see a lot of G3/J3 amongst top players, notably the Championship game between @Daaras and @Ghostglider had a J3 DOW on Allies except USSR, followed by I3/G4 Russia DOW. Late DOWs seem to be fairly common (although I need to comb through many more threads before I have statistics to back that up).
I personally have begun to favor the J2 after working on my “new” strategy, which I cannot take full credit for. After seeing @pacifiersboard using the cruiser/marine at Carolines on J1 taking New Hebrides against @mikawagunichi , I began to contemplate how this might be used effectively.
One of the stickiest points in my usual Japan strategy is the massive Allied fleet that inevitably seems to coalesce off the coast of Queensland. This fleet is constantly threatening the rich DEI and their NO, as well as allowing ANZAC to buy boats & planes, and easily maintain an income of 16. Denying US the opportunity to move a large fleet to sea zone 55 allows Japan to deny at least one of these Nos, and usually both very early, as well as using a sub or 2 to convoy the 3 IPCs in Victoria & NSW.
I have used a variation of this to open several games now, and has been quite effective in the Pacific theater. A bid of 6 to Japan for an extra transport is quite potent, but not entirely necessary for this strategy. Indeed, you might argue that putting the bid into Europe might be a better use.