The delays in fiat withdrawals continue, particularly for USD. Since these are not properly disclosed (or even the need to pay the 5% fee for a "manual withdrawal") on the website, I think one could go ahead other incidental damages and certainly interest on the amounts involved for the length of the delay.
The fraud-like aspects, not properly disclosing, could be strong grounds for additional damages (at least if Japanese law is similar to the US in this regard).
Please continue the lawsuit. They need to pay damages for the delays and it will serve as a warning to others.
A lawsuit which isn't going to be determined for a very long time isn't going to influence the behaviour of other services now. If it was, then MtGox would already have changed its behaviour as conversion, negligence and breach of contract are all causes of action in the Cartmell et al lawsuit against Bitcoinica.
It's also only going to "serve as a warning to others" at some time in the future if the plaintiffs actually prevail. If they don't, then it's only going to further entrench undesirable behaviour by Bitcoin services.
It's also worth remembering that while you can sue anyone for anything in the US, that's not the case everywhere else. Before you even consider litigation in a foreign jurisdiction you need to first establish how its legal system
differs from your own. What options are open to you in the US is pretty irrelevant if the US isn't the jurisdiction involved. You need the advice of experienced litigators in the jurisdiction where you'll be filing rather than guessing about what might be possible under a legal system with which you're unfamiliar.