Order of Hermes isn't bad or anything, but it does break 2nd edition's streak of gradually improving splatbook quality. The culprit here is probably the fact that in Mage canon, the Order of Hermes is full of shit. I mean, all the Traditions are full of shit to one degree or another, but The Order of Hermes is the one that gets repeatedly called-out in-setting as being the most full of shit. Because they are Mage's designated "pompous braggart" faction, they need to be able to back it up at least a little, if they are to have any degree of dignity.
But, of course, that would be impossible. In both the broad strokes and the specific details, the Traditions are balanced against each other. The system simply isn't interested in providing the mechanical widgets necessary for asymmetrical factions. Everybody uses the same nine spheres in the same straightforward way (though, hilariously, this book suggests that an early in-setting
prototype of the Sphere system had 324 Spheres - make that game, you
So The Order of Hermes is far from unique in that rules make a lie of their fiction. The Dreamspeakers get it almost as bad. They have no intrinsic advantage in dealing with the spirit world. Their way of doing things still follows the same "extended Arete roll" pattern as all the other mages. To a certain degree, this is something you just have to buy into if you're playing Mage. Dreamspeakers are the Spirit Tradition, Cultists of Ecstasy are the Time Tradition, etc, so even to the degree that player characters suffer no disadvantage from learning Spirit, Time, et al as the "wrong" Tradition, you can kind of assume that as a group, the NPC members of the Traditions have a particular density of expertise.
Nonetheless, the Order of Hermes mandates an intense and extended academic training, and the book is not at all clear on why. The Order looks down on other Traditions because they don't undergo the same rigorous training . . . but they quite objectively have the same powers. Order of Hermes, the book, divides magic into three tiers of sophistication and claims that the Order believes most mages only have access to the first level. But how could they believe something like that, unless they were extraordinarily full of shit, even by the high standards set by Mage: the Ascension.
It can probably all be traced back to the Ars Magica connection. I don't count it as a flaw that the World of Darkness' Order of Hermes shares a complicated history with an entirely different game line. It's actually a rich source of detail. However, in the Ars Magica setting, the Order of Hermes basically serves the exact same function as the Council of Nine Traditions. In one world, their claim to be the governing council for all magic and guardian of advanced magical knowledge is completely true. In another, it's hugely misguided. And the similarities between the settings often serve to obscure that difference, to the WoD Order's detriment.
But assuming that Mage should exist, and that there is something to justify the Order's swagger, Order of Hermes is a decent book. The Hermetic mages have a historical heft that feels authentic and there's an admirable diversity in its various factions and specialties (my favorite was House Shaea the cat-themed feminist linguists operating out of Egypt). I can't say that's it's completely successful - it needed to make the Order of Hermes into something more nuanced than "the asshole Tradition", and it's probably the least essential Tradition book since Verbena, but I enjoyed reading it, and that's not nothing.
Ukss Contribution: One of the Houses of Hermes is called "House Janisary." It budded off from the historical Janisaries at around the time that they started to dominate the Ottoman Empire (as befits the Order of Hermes' preference for mages of aristocratic background). It might be interesting if one of the evil empires of Ukss had a caste of slave-magician/soldiers.