snagged the Brew Kodo, he also landed the flying horse mount from the Headless Horseman. This mount is one of only a handful flying mounts that have a ground only mode, allowing them to be used in no-fly zones (such as Dalaran, and outdoor flagged dungeons). In principle, I guess I would rather have landed either or both on my mage, who is my actual main. Then again, Greenwiz has his share of shiny rides, while the warrior has only a few, so they might as well be unique.
I haven't quite decided what I'm going to do for the rest of the holiday. There's no guarantee that I'll land the mount on my mage, even if I do the event every day from here on out, and he doesn't need anything else that I can get from the Horseman. By contrast, the warrior might in principle want some of the loot and achievements, but he's already got the event's biggest prize. I guess the bottom line is that I won't cry if I miss a few days.
Otherwise, the event has not changed or improved all that significantly since the 2008 edition. There's a vaguely amusing achievement line to visit all the Innkeepers in the world for some gold and candy, which is probably worthwhile only if you're dying to see the un-shattered landscape one last time. There's a PVP achievement that can probably be earned most efficiently by joining a Wintergrasp battle and hiding somewhere near the combat. There's a fire-fighting event in the newbie towns that will almost certainly be won or lost without that much intervention from you individually. Finally, the once per real world hour trick or treat mechanic is back in full effect, with at least one achievement that can only be obtained via a lucky drop and a few others that similarly hinge on the random treat bag.
Personally, I don't think this type of system has any place in a short seasonal event. If Blizzard wants people to fail to complete the event due to the vagaries of the RNG, the achievement in question should be tied to a daily quest so that it does not penalize players for failing to stay up just one more hour to see if next hour's treat bag will have what you need. Talking to an NPC is not fun, it is not challenging, and it only fosters an image of addiction that the industry is generally working pretty hard to avoid when they're not stumped to think up just one more timesink.
Somehow, Blizzard found the time to revise a similar debacle out of the Valentine's event between 2009 and 2010. (The 2009 version was so much fun, I literally signed up for an EQ2 trial and rolled up the character who became my main, checking back with WoW to once an hour on the old laptop to see if I'd win the candy heart lottery.) I can only hope that the Halloween version manages to make similar progress by 2011.