Which part? Just about all of it. What's not to love.
Buffs are plenty for almost all classes and lower cooldowns on many major spells.
BoA Helm & Shoulder enchants from faction usable at the correct lvl means the endless grinds are over. "Sons of Hodir" grind anyone? What's not to love? Well maybe less gold in your pocket from less of the grind. With my faction exalted Paladin I can buy any alt their max Helm & Shoulder Faction Enchant if need without them enduring the endless grind. However I would of grinded it anyway, this just saves lots of time.
Shadow Priests getting lots of Buffs. Mages getting permanent summoned pets. Hmm might be worth leveling my trusted banker Shadow Priest for the fun or a Mage. Who knows though.
Huge bump in Northrend faction rep gain. Yeah, awesome, less faction grind! Who doesn't love less grinding. Still kinda Meh! I would be pleased with increased major city reps being available from all faction cities.
Hunters pets take less XP to level up, awesome go to love that. I know I do too with a stables full of pets on my Hunter.
Shamans get to play more with their Totems. Yeah Shamans are fun!
You get to finally kill the main man Arthas because your so bored of everything else.
Game getting so easy even a idiot can play it.
Ok, back to playing WoW....