An honest assessment from the perspective of a long time WoW player, for those who are considering making the jump.
As is the case with any MMORPG game, it is almost impossible to assess the value of the game after playing it for 3 days - I have played a Tempest of Set (caster/healer hybrid class) up into the mid level 30s, as well as several other classes into the mid teens - and there is probably an entire years worth of content within the game, and undoubtedly more soon to come in patches.
That said, from my limited experience I could briefly summarize AoC as a beautiful, immersive game world with an extremely addictive combat system, that is undermined by an awkward and unwieldy interface and numerous bugs.
To begin with the positive, you simply will not believe that this level of sophistication exists in the graphics of an MMO. Every character, tree or blade of grass has an accurate shadow, the lighting is all highlighted by beautiful bloom effects, all of the textures have an incredible level of detail, the maximum view distance is astounding, and alot of effort obviously went into the character animations which feel very fluid - However don't expect to run this game on anything near the maximum settings unless you have a top of the line gaming rig. Although I played on an up to date computer, I was actually also able to run it on a computer which just barely met the minimum requirements, which is a pleasant surprise when the requirements for games are often understated. The sounds as expected are equally impressive, and the soundtrack is a pleasure to listen to, although you will probably have it turned off eventually anyway.
The combat system, which is one of the biggest draws to this game, definitely lives up to the hype. The animations are all very visceral and you maintain a feeling of momentum when leaping into combat and into a sequence of attacks. There is no auto-attack system; and the shielding system ensures that you are always actively participating - no getting up to make a sandwich while your pally swings away with his seal for 30 seconds. Scoring the rare fatality and lopping someones head off is always an oh s***t moment. The spell animations are all awesome to watch, however it seemed to me that there is so much more fun to be had as a meelee class in this game, as the spells are all fire and forget like any other MMORPG. There is some sort of interactive spellcasting system called spellweaving, but it doesn't come into play until the later levels, so I doubt any players can yet testify to it. I can guarantee you however that the multiple facets of the combat system (and I encourage you to do some research about the combat system within this game) will guarantee a far more skill-based game than WoW, especially when it comes to PvP.
The greatest failing of this game however, especially coming into the game from WoW is the interface, which is really unbearable. The quest system, while it conveniently displays the location of your objectives on the map, does not have an indicator of whether you have completed a quest or not - so this leads to significant confusion. All of the panes - the skill pane, the inventory, the feat trees (think talent specs), etc, take up almost the entire screen, when realistically they could have been trimmed down to a quarter of the size - and whenever you loot a body the screen becomes filled with these annoying black bars of text - leading to you often being completely blinded by unnecessary information. The friends interface is tiny and does not provide adequate information about the players on it -also, there is no guild list, instead all guildies are automatically placed on the friends list, which makes locating your friends a real pain. Don't expect anything near the amount of feedback about your group that you get from WoW, there is no system for locating your group on the map, and the grouping interface is limited to a tiny list of health bars in the upper left hand corner. The chat system is also a real pain in more ways than I care to discuss in this review. There are dozens of other interface annoyances and bugs that you will quickly discover. These problems can all be resolved easily, however any experienced MMO player will tell you not to believe any developer's promise until you see it with your own eyes. Considering that Funcom has stated that there will be NO support for user created interface mods, this is a major concern, as the interface in games such as this have a greater impact on the gameplay than you would think, especially when it comes to the endgame.
There are also a large number of small graphical glitches and gameplay bugs at this stage, none of which have been game breaking for me. At absolute minimum settings, the game appears out of focus (like being drunk in WoW), often textures don't render unless you are right next to an object, and I experienced an issue with my destiny quest (class quest from 1-20) that a GM had to resolve for me. Many players have complained about the game randomly crashing.
There are over 200 players happily tinkering away in my guild at this very moment however, most of whom haven't complained.
There is one "racial PvP" server, but for the most part PvP servers are free for all at this stage. I play on a PvP server and I am constantly being ganked. I would argue against the value of free for all PvP in MMO's, but this is no fault of the game itself, and naturally your mileage may vary.
Don't let these relatively minor points of contention discourage you however - I encourage you to look into the seige warfare, city building, and mounted combat systems, none of which I (nor any players at this stage) have experienced, which will give new life to the game at max level. This is an MMO which has experienced so far what has been one of the smoothest launches in history. Although it is plagued with interface problems and bugs, I am confident they will be resolved soon. This is definitely one of the most promising MMOs since WoW was first released. Check it out.