I really liked the shiny bits on the Alliance bike, especially the emblem in the front and would have liked to see it translated into the game. I could have done without the treads or scimitars. The Horde bike typified everything about the Horde: brutal, loud, and redolent in red and black.
People have commented on the Horde players. I've played both Horde and Alliance since the second beta (remember before Taurens had mounts?) and there are rude people on both sides and genuinely nice ones as well. I suppose it depends on what you're trying to get out of it. People who focus solely on the end game content and raid all the time are very different from people who play as a family for fun. Raiders are brusque, impatient, arrogant and judgmental. Casuals are uncoordinated, inattentive, are frequently interrupted by real life, and sometimes a bit thick. Raider are also dedicated, professional (if such a term can be used), and display ingenuity and perseverance. Casuals are friendly, accepting, patient, and easy-going. I am of course speaking in generalities but I just wanted to highlight the dichotomies in the game. You can find both to be true for Horde and Alliance, raiders and casuals alike. All in all, I prefer the Alliance. I love their take on Dwarves (I especially like the Bronzebeard brothers and the Wildhammers), and I love the technological insanity of the Gnomes.) I still have a lot of respect for the Tauren on the Horde side. They seem to have the wisdom the other races lack.
I have always found it more interesting that while Blizzard has favored the Horde for so many years, to include that pathetic display at Blizzcon 2011, that story-wise The Horde is portrayed in a much more negative light.
Everything from the Forsaken concocting plagues and using Valkyries to create more undead (by killing everyone else), to the "True Horde" going raving nanners and Garrosh killing Cairn Bloodhoof (don't give me that garbage about how it was a mistake and Magathra Grimtotem poisoned Garrosh's axe. The only reason Cairne was in combat with Garrosh in the first place was that he was killing druids), the Blood Elves enslaving Naaru and turning to Burning Legion as a new source of magic, to the Goblin's strip mining and pollution all show the greed and shortsighted goals of the Horde. The only Horde races portrayed as noble are the Tauren and Pandaran (which I consider neither Horde or Alliance). I have a lot of respect for Thrall though; He just wanted to make a home for his people and return them to their shamanistic roots. Too much to ask for I guess.
In contrast the Alliance's worse crime is leveled at the Human King Varian Wrynn, who has been known to call Orcs mongrels and dogs and see them as subhuman. Not the best qualities to have but as far as the story goes, he was enslaved by Orcs and made to fight in a gladiator Arena. I don't think I'd like them much after that either. He really got mad in WoLK going as far as to say "Kill em all." In Cataclysm the Ally/Horde War was renewed and he pretty much kept that same tone which was also mirrored in Garrosh. In MoP it seems like events have transpired that have tempered the Kings Anger. If you read the comics and books, he does something that takes away some of that anger and balances him out. His overriding emotion in MoP is concern for his son. If anything the character Admiral Taylor has supplanted him as prime Jerk of the Alliance. In fact if you play the Scenarios in MoP and listen to the King's dialogue he has grown much wiser and more concerned with unity in the Alliance.
That all being said, as much I as love the lore and story, it's all just fantasy from a pretend game. I'm sure a diehard Horde player could spin a tale putting his favored faction in the more positive light too. Rivalry is fine, but when it spills out the fantasy world and into the real world and is encouraged by the makers of the fantasy world, it's not cute or thematic. It's thuggery.
Now if you'll excuse me, I have to get back to playing Hello Kitty Island Adventure.