I've been a fan of oriental milieus for role-playing for a long time. I've played various incarnations of 'Bushido', which I keep for source material, and the 'Legend of The Five Rings' is prominent on my bookshelf.
I may not need them anymore.... I have Oriental Adventures now.
First off, the artwork and presentation are on a par with the Forgotten Realms Sourcebook. Yep, it's just that good. Most games that try to add an Asian flavor just try to tweak the ordinary fighter/wizard/cleric/thief classes a little and call them something else, like samurai or ninja. Worse, they make the Asian PC's virtually unstoppable against those poor elven and dwarven sods in Western games. Not historically accurate, or really that broadening to play. The samurai and other classes are very well fleshed out. Love the rules on augmenting a family katana, too; it makes good sense how they do it, and makes it unnecessary for the DM to alter his treasure tables if he has one samurai character in a party.
The history section is interesting, and based on L5R, but I'm more interested in historical Japanese and Hindu milieus. That said, the section on weapons is very good, and doesn't have just one or two weapons. The special rules on the sodegarami and the sai really capture the reason for the weapons. Some nasty Chinese weapons make the cut, too. (So to speak....)
The spell lists are great (although I have a certain fondness for Bushido's "Stench of Kim-Chi" spell), and very Asian in their flavor and execution. This way, a wu-jen isn't just a standard D&D wizard with a couple of odd characteristics and different names for his spells.
The feats and prestige classes are uniformly well balanced and interestingly presented. The monk classes, like the Tattoed Monk, are inspired, and fit the flavor well. As a GM, I didn't see anything in them that warranted disapproval, or (*gasp!*) being banned from the games I run. All in all, very well thought out.
The extra races are a treat, too, and, like the rest of the book, very well balanced, and they fit well within Asian areas of concentration. I especially like the Vanara.
All told, an excellent supplement, and well worth the dollars I laid down for it.