It was different right from the start of Northshire Abbey, the kobolds and wolves have been replaced by Blackrock spies and something else I can't remember right now, the fields across the river where there used to be a grape-collecting quest are now aflame and need to be be extinguished. There are two new flight masters in Elwyn Forest alone - one at Goldshire and another at the Eastvale Logging Camp and as if that's not enough, the first time you travel from Goldshire to the Logging Camp you get to ride on a Stormwind charger. Don't even talk to me about how little it costs to buy your first mount, and at level 20 to boot.
We were really impressed by the main quest arc in Westfall. There's a shock discovery as soon as you enter the zone - murder most foul! - and many of the quests tie into the storyline nicely. I was surprised at the nostalgia I felt when we saw how much Sentinel Hill had changed, and I'm sure those feelings will recur as we get through more of the vanilla-WoW zones in the days to come.
There were many nice touches of old, familiar NPCs having moved on in the years preceding the Cataclysm, Guard Parker is now a Watch Captain, and his sweetheart Darcy is now his wife and they have a child; Lieutenant Fangore got a promotion as well... so far so good, looking forward to the rest of it!