- Classes now start with a specialization. Paladins start as Retribution, Druids start as Feral (and start the game in Cat form, no less), Hunters start as Beastmaster, etc. I think the other specializations unlock at level 10. Overall, I think this is a good idea. There's no forgetting to specialize, and no "generic" abilities which are only used in first 10 levels. You also don't get two abilities that don't synergize, because they are meant for different specializations.
- Judgment has a new animation. You throw a golden hammer at the enemy, and the hammer returns to you. It also sometimes chains to a nearby enemy, but I can't tell if that's intentional or a bug.
- I think the Hammer of Justice animation changed. A giant hammer drops from the sky on the enemy's head. I don't really like it. I miss the simplicity of the current spinning rising uppercut animation.
- The default nameplates have changed. They're cleaner, and enemy health is represented as a thin red line, instead of a fatter bar. There's also small health/mana/resource bars in the center of your screen under your character. These bars only appear in combat, and fade out otherwise. I really like these new nameplates.
- The quest helper minimap graphic has changed. It's now this transparent outline instead of a shaded area.
- There's a nice animated flair on the XP bar when you get a large amount of XP. It's snazzy.
- The initial class quests that send you to your trainer are gone. I guess it makes sense since the abilities have all changed. Still, it makes me a little sad. I liked that little nod to your class right at the start, with the notes expounding the philosophy of the class.
- Armor starts as the max armor type. Paladins get plate, hunters get mail, etc. The item still looks the same as previous, like mail or leather. This is a bit weird with mail armor that looks like leather (those night elf shorts you always get), but plate that looks like mail looks decent enough.
- Otherwise quests appear to be all the same as live. For low levels, it looks like only mechanics changes.
I didn't poke around a great deal, but these are some smaller impressions of what you can expect in Legion at low levels.