The best (i.e. most populated and well-scripted) private "Blizzlike" vanilla and BC servers I've found are the level 60 Warsong and level 70 Archangel servers run by the people at wow-one.com. By default the XP gain rates are 12x and 14x, respectively, but you can change your rate to 1x from the account panel on the site. I think that they ask for you to vote for them on one of those sever ranking sites but it takes like 10 seconds. Yes, it's free to play.
On the 60 server, ZG, AQ20, MC, Ony, BWL, AQ40, and the 5-man dungeons are all fully scripted. There are only three bosses in Naxx still not available. The server population peaks at
~3000 players daily. There are slightly more players on Horde.
The 70 server isn't quite as far along but still has all of Kara (minus chess event), all 5-mans and heroics, all of TK, and 5/7 SSC bosses. Arena is in S2 right now. Server pop hits
~2200-2500 players daily, and like Warsong, there are more Horde players.
They do have another new-ish 60 server that is 1x by default, Emerald Dream, but there isn't nearly as much content available, the population peaks at ~1000 or less, and development seems to have slowed down there.
As for how "Blizzlike" it truly is, I was one of those elitist jerk hardcore no-lifer feggets back in retail vanilla and BC, and I have no real complaints as far as how true to the experience the servers are. You can find videos of boss kills and PvP videos from these servers all over YouTube if you want to see for yourself.
Here and there you'll come across some minor bugs but nothing game-breaking. The bugs that bother me the most are the bugs that affect PvP. I do remember a handful (like 5 or less) of broken quests when I leveled on the 70 server last year but they are constantly fixing stuff. You can check out their bug trackers for both the
60 server and the
70 server if you're really curious.
I hear Molten WoW also has a nice, high-pop WotLK server too but that's about when WoW went to shit for me.
Anyway, I've been playing on these servers for like two years, so let me know if you guys are curious about anything