Classic WoW was demo'd at Blizzcon this year, both for attendees and virtual ticket subscribers. As I am neither, I had to rely on reports from other people on the internet. Blizzard also announced that it would launch in Summer 2019, which is a little sooner than most people expected.
From all I've heard, Classic seems to on the right path, and hitting all the notes that people want. There are still minor inconsistencies, but they seem to be around things like tauren melee range, or the exact timing of warlock summons. Which are are relatively small issues.
The two bigger areas of controversy are sharding (multiple copies of a zone) and trading loot. There was some dismay that Blizzard was sharding the demo server, and will be sharding at launch.
In my opinion, Blizzard has to shard at launch. There's going to be a ton of tourists, followed by a steep drop in population. If a healthy server has 5000 people, it will probably need 15,000 at launch. If they open too many servers, three months from now there will be many dead servers. Just like SWTOR's launch. So sharding is the best solution.
The other change is that Blizzard will allow loot trading to other people in the raid. This is primarily so that people can fix mistakes with loot distribution, like master loot misclicks, rather than filing tickets with Customer Service. I think this is reasonable, and probably a good idea.
All in all, Classic WoW looks like it is on track. Then we'll see if people really want all those inconveniences, or if it is just nostalgia.