Just to chuck a different opinion in, I've got to say I prefer AoC over WoW, maybe it's the newness of the game, or maybe I've just become bored of WoW, but I am definitely enjoying AoC a lot. Strangely it's some of the points listed here that I find better in AoC.
PvP is excellent in AoC, so much so that I'm playing my main on an RP-PvP server, with WoW I hated PvP so much that I played on a PvE server, it just feels like so much more fun. I'm not ashamed to say that I'm usually quite rubbish at PvP, but I enjoy the fighting in Conan even if getting beat.
I started getting a bit sick of the graphics in WoW, I know they were great for being able to run it on a low end system, but I'm glad they have gone for a more detailed graphics system because I've got quite a nice system and it's great being able to put nearly everything on max settings and have a great looking game to play, especially if your going to be spending a long time playing it. Also the performance has been great for me, I've seen the posts all over the official forums about crashing, bugs, poor performance etc, but I must be really lucky because it just runs fine for me.
I also love the combat system in AoC, I will admit to being worried that there was to much button pushing involved, but three weeks in and I'm still loving it. I think the idea of different directional hits and shielding is great as is the combo system for getting abilities to work, it just seems to make combat feel much more involved for me.
Maybe my opinion will change, I certainly haven't seen all of AoC by a long way, infact at the minute I'm taking each class up to lvl20+ just to see which one I like, I'm also taking my time and enjoying the game, so far I've not found and problems with lack of quests, items or game content. I'm sure that will change once I pick a class and start getting into the 30's and 40's but then the game has just launched and I'm sure there will be plenty of content added over time.
Finally, a lot of people have problems with the instancing in AoC, it doesn't bother me at all because I was used to it from playing EQ2. I've found that it has never hampered my game and there have always been plenty of people in whatever instance I've been in, besides you can change instance to be with friends. So yeah, maybe I'm just getting caught up in the newness of it all, but it's finally got me to cancel my WoW account after a long time.