Re-reading, Oct. 2011:
I probably read this in the late '80s/early '90s, shortly after it came out, and all I can remember is being not terribly blown away by it: not much else stuck with me. On re-read, it isn't impressing me any more than the first time. Robin Hood's is a story that you can figure pretty much any fantasy reader/movie fan knows - Robin, Little John, Much, Marian, Will Scarlet, Alan a' Dale, Friar Tuck, Sheriff, Richard the Lionheart, and a cast of dozens. Oppressed Saxons, greedy Normans, etc., etc., etc. The only surprises lie in how an author or filmmaker chooses to spin the details.
In this version, Robin is a poor young man, working as a forester as did his father. There are vague references early on about his late father having been connected to some sort of populist rebellion, the scant memory of which is purported to be the means of stirring the smallfolk to support Robin -- and, by association, inspire them rise up against their Norman masters -- when he is forced to flee into Sherwood Forest after having accidentally killed a man (see, in this version, Robin is a barely adequate archer who *meant* to shoot the guy in the leg, but instead skewered him right through the chest. Ooh, such a huge twist, to downplay the hero's legendary skill!)
If you're looking for buckle and swash, this ain't it. Robin is a reluctant symbol whose primary concerns are a) not to get caught by the sheriff/any of his henchmen and b) to prevent any of the dispossessed smallfolk who keep showing up in Sherwood from being caught, either. He spends a lot of time brooding, trying to talk his people out of carrying out some reckless scheme, and repressing his feelings for Marian (who as a "well-born" woman obviously should not be hanging out in the woods with the scruffy likes of him.)
I think the point of this version is supposed to be that the Middle Ages were hard and most people's lives were nasty, brutish, and short. The hideaway in Sherwood would have been much more as portrayed here - a rough, barely adequate shelter with bugs and mud, insufficient food most of the time, and a constant fear of discovery - than, for example, the "Robin Hood, Prince of Thieves" version with treehouses and dozens if not hundreds of happy, well-fed villagers, the location of which is so unexplainably obscure as to require a traitor to point the sheriff's men in the right direction. If anything, I have some of the same quibbles with McKinley's version, as the initial volunteers for the band of merry men seem to have suspiciously unduplicated and useful skills (carpenter, leatherworker, fletcher, etc.) And is there an endless supply of that badly-dyed green wool? because it amazes me that people are still wearing it after more than a year living rough.
Note: Robin McKinley is still one of my favorite authors - I think this was one of her earliest books, so we'll chalk up any issues to inexperience.