The panel "will be able to summon any person or organization to testify, or to give it information in some other fashion, on any issue it deems relevant," except that it can only access military files "directly relevant" to the operation, including those from a separate, internal IDF probe being conducted contemporaneously. It can, however, request additional inquiries if it finds the IDF probe insufficient. Finally, all statements given to the commission will not be admissible in any legal proceedings, to encourage candor.
Sounds like a pretty robust investigatory panel to me. But I still maintain it will mostly be irrelevant, because what people want out of their "investigation" is either an indictment or an exoneration (depending on their alignment). Well, that might not be totally fair -- I'd be surprised to see any significant protest from the pro-Israel folks if the country's own panel decided to excoriate the operation (this is purely a matter of relative credibility -- the same conclusions, reached in identical language, by an international body would be met with outrage). But if the panel mostly exonerates the Israeli behavior (and I suspect it will -- the legal and factual issues are simply too unclear to warrant broad-based condemnation), the anti-Israel crowd will pitch a fit no matter how independent the panel objectively was. And while it will claim that it's real objection is that an Israeli panel can't "investigate itself", I'm honestly doubtful they'd react much differently if an international panel reached the same conclusions in identical language (we'd just shift to complaints about the all-powerful
But that's all counterfactual. The point is, there is a panel now, it looks pretty robust and independent, and it will issue a report at some point. And my conjecture is that this report will have virtually no bearing on anything.
UPDATE: Ha'aretz's editorial doesn't seem to think this panel is that impressive at all. But I'm a little confused -- the editorial says the panel has no powers at all, but the article seems to make clear that it has significant subpoena power.