Not my words but well written.
"Great, they are going to make Classic servers, but the question is, how Vanilla will they be? Put another way, what ruleset version will they launch with, one from Jan 2005, when the Molten core was the only raid, or from Oct 2006 when players were fighting their way towards the 4 horseman.
So much happened between those two dates. The battlegrounds were added, along with entire zones like Silithus. there was the world event to open the gates to AQ40, and the difficulty of the 4 horseman to this day remains as one of the longest encounters to stand before being beaten. (7 weeks)
In vanilla WOW, shaman only existed on the Horde side, while Paladins were exclusively alliance, one factor which lead to people claiming Alliance had a huge raid advantage because of this.
So many changes during those two years, they really were a form of progression server all by themselves, so again, where should classic servers start, and should there be any progression as was done the first time around?
There will be temptation also to include features from later expansions, perhaps adding in Death Knights, or additional races such as Dark Elves. Or since most raids were 40 man in Vanilla, (there was AQ20 ) will there be any temptation to add in some of the 25 or 10 man raids from BC or other expansions? Will they add convenience tools such as dungeon or raid finders?
When the DAOC classic server team ran their first iteration, they originally started with a baseline 2002 version, but they started adding in convenience features, realm abilities and even classes from later releases. They even created their own new content zone with totally new rewards and skills from it.
Eventually they decided these changes diluted the "classic" feel of DAOC, and was causing a number of challenges in trying to upgrade to the SI expansion. (Will Blizz ever want to progress the classic, servers, a question for a different thread I think.)
So they eventually shut down the server for two years, and when they rolled out again, it was version 1.69 in it's purest form, which was great, but even then withing 6 months they started making a "few" changes to make more Battlegrounds available earlier and provide players with more rewards from PVPing.
It will be very interesting to see what decisions Blizzard makes in deciding exactly how true to their roots this version stays, because as others have noted, it will get stale pretty quickly if they launch a single point version and then let it stay stagnant on that single point in time. In the DAOC classic servers, it started out strong with a packed 4000 person server, by July fewer than 500 were online at any one time during US hours."
Read more at
http://forums.mmorpg.com/discussion/469360/the-easy-decision-to-create-classic-servers-was-just-the-beginning#ERkj71TgdE7giBg2.99