Vanilla WoW was awesome. I have to say that.
I went back to it on a 15 day trial and it's been transformed into something that I wish not to play anymore. It was good, but IMO it's not anymore.
Just, whatever you do, don't try a private server before you go onto the blizz servers. all Private servers are shit, full of bugs, and usually can't handle that many people on the server, meaning that your chances of finding a party to do anything are slim to none.
Of course my opinion is just one of many. You may enjoy WoW, since you aren't jaded from what it USED to be like. Me? Well, you know what they say...you can never go home again.
Also, WoW is addicting, yes, but only for the first year or so. After that, it's a little easier to tear yourself away.