i did this a while ago. here is whats going to happen. you were bored with WoW, which is inevitable when your friends stop playing and you already have everything and hate making 10 alts.
When you start WHO, you will be excited, public quests, battleground Qs from anywhere in the world, questing, etc. The early levels are a blast as you can level fast by just doing the BGs. Up to level 20 or so it will be like this. It will slow down as you approach 30. Like any mmo though, the last levels take longer, but you will make 40. Maxing your reknown level to 80 will take massive amounts of time however. Getting geared in tier gear is not that difficult. So, aside from reknown levels and the gear that goes with it, you can quickly catch up to other players in many aspects of the game, just be sure to join an active guild.
Now the key with WHO, is you MUST join a high population server. the game is entirely dependant on high population of active players. The population must also be close to equally balanced between order and destruction. Twice i was on a good server, then one side starts to dominate, the other side's players quit or reroll on other servers, and soon enough you find there is no one to fight against so you also must reroll or wait until they allow srever transfers to or from your server. Also you better have a good pc or you will sputter out and die when the giant keep siege battles happen and its hundreds against hundreds.
After seeing two servers become population dead and/or horribly imbalanced, i would not reroll again so i quit WHO as well. Just as well, i really cant devote that much time to any MMOs anymore. I do however support WoW minis which is good fun.