I think the committee report is generally solid. It's analysis on the overall legality of the blockade is unquestionably superior to that forwarded by the UNHRC's report, which (and this is true regardless of one's ultimate perspective on the conflict) was frankly an embarrassment to the legal profession (how one even tries to undertake a proportionality analysis without even mentioning the objective in question, see paras. 51-61, compare Palmer Report pp. 38-45, is a mystery). So that's good.
Of course, I remain exceptionally dubious of the utility of these reports or the international law frame at all. The Palmer Report had been delayed several times because everyone believed it would only hurt rapprochement efforts between Israel and Turkey (Turkey is hell-bent on a full apology and an end to the blockade, which Israel is far less likely to do now that a high-profile commission has deemed the blockade legal and vindicated many, albeit not all, of its actions). Folks opposed to Israel's actions will simply cite the UNHRC report instead. Israel knows that, which limits whatever benefits it might reap from citing the Palmer Report. The conflict is political, and will be resolved politically. Whatever formal authority the Palmer Report has (and I'm not sure it has much anyway), formalism is not and should not be the primary lens for examining the issues in this controversy.
UPDATE: This older post by Kevin Jon Heller offers a good foil for some of what I'm trying to say here. Unlike the UNHRC opinion, Professor Heller provides a solid, well-reasoned argument for why the blockade is illegal (which isn't to say I'm necessarily persuaded by it; indeed, Professor Heller is admirably forthright about his uncertainty on the question). Professor Heller's basic claim is that the conflict between Israel and Hamas is not of an international character, and that international law does not contemplate the use of blockades in non-international conflicts.
The Palmer Report considers and rejects that point, instead holding that the conflict between Israel and Gaza is, for all intents and purposes, "international" for the purpose of the law governing blockades:
The Panel now turns to consider whether the other components of a lawful blockade under international law are met. Traditionally, naval blockades have most commonly been imposed in situations where there is an international armed conflict. While it is uncontested that there has been protracted violence taking the form of armed conflict between Israel and armed groups in Hamas-controlled Gaza, the characterization of this conflict as international is disputed. The conclusion of the Panel in this regard rests upon the facts as they exist on the ground. The specific circumstances of Gaza are unique and are not replicated anywhere in the world. Nor are they likely to be. Gaza and Israel are both distinct territorial and political areas. Hamas is the de facto political and administrative authority in Gaza and to a large extent has control over events on the ground there. It is Hamas that is firing the projectiles in Israel or is permitting others to do so. The Panel considers the conflict should be treated as an international one for the purposes of the law of blockade. This takes foremost into account Israel’s right to self-defence against armed attacks from outside territory. In this context, the debate on Gaza's status, in particular its relationship to Israel, should not obscure the realities. The law does not operate in a political vacuum and it is implausible to deny that the nature of the armed violence between Israel and Hamas goes beyond purely domestic matters. In fact, it has all the trappings of an international armed conflict. This conclusion goes no further than is necessary for the Panel to carry out its mandate. What other implications may or may not flow from it are not before us, even though the Panel is mindful that under the law of armed conflict a State can hardly rely on some of its provisions but not pay heed to others. (p. 41, para. 73)
This sort of analysis appeals to my legal pragmatist streak generally. And specifically with it is hard to argue against the Palmer Report's conclusion that the conflict bears the "trappings" of an international one in terms of actually describing the hostilities between Israel and Gaza. Even to the extent he's right, Professor Heller's analysis is another example of formalism and categories triumphing over descriptive and normative realities. That's not a strike against Professor Heller -- he's doing what lawyers do. And perhaps in a world where international law was a stronger force and it didn't seem like all aspects of the Israeli/Palestinian conflict were treated as sui generis anyway, it might be more important to rely on staid legalisms (though I'm not sure why participants in non-international conflicts should never be allowed to resort to blockades anyway. Their omission seems more a function of the rarity of situations where one would make sense -- Israel/Palestine really being "unique" in this regard -- than the result of some normatively sensible distinction). But that isn't our world, and in the world we live in, the Palmer approach seems far, far more reasonable.