The most important thing you should note is that there are no official beta keys. Blizzard opens the gates to their betas by granting access to your account — not sending you a beta key. If you’re in the beta, you’ll be able to download and play the WoW Classic client from your Battle.net launcher. If not, you aren’t in the beta. It’s easy to be tricked into thinking you’ll get a beta key from an email that looks like it’s from an official Blizzard address, but don’t believe their lies — they’re all fake.
The Horde levels 50-60 guide has been rewritten and revamped. My 1-60 Horde leveling guide is now completely updated for the 1.12 Drums of War patch. As you can see it is about 15% larger than the 40-50 guide (single largest guide page yet). There is also a lot of route changes. I moved the entire Silithus section from level 55 to level 58, which allowed me to include a lot more quests for that zone. There is also a lot of other improvement to the route, including adding a lot more quests into the guide, mostly from Moonglade, Silithus and Eastern Plaguelands. This will make the final level 59 grind much shorter.
That's not to say that everyone has an unrealistic vision of what vanilla WoW was like. There were already plenty of people on the WoW Classic forums pointing out that perceived bugs are just recreations of the original game. And as noted before, a flaw to one player is a key component of the original positive experience to another. WoW Classic will surely please plenty of purists in spades. But this goes to show that it won't be for everyone who has fond memories of the game circa 2006.
I made some route changes to the Horde levels 43-44 sections. I have swapped 44 Dustwallow Marsh with 44 Desolace (the entire sections). This allowed me to do Deadmire (at lvl 43 instead of 38) and then go stop at TB to turn in Deadmire + The Black Shield at the same time, then fly quickly to do the Desolace stuff. Doing 44 Desolace is now mandatory because I think its faster with the new routes. This will also make the level 53 grind much shorter. I think these were great changes.