Having a few mmorpgs under my belt (Daoc, Eq, Eq2, WoW), I can honestly say I've never had this much fun with combat. The active combat system is a lot of fun. Essentially, the active combat system eliminates auto-attack and implements directional attacks (lower left, upper left, head, upper right, lower right) to hit your enemies with. NPCs, as well as your self, can shift where you would like to reinforce your general defense.
E.g. x = player, < = guard left side, ^ = guard head, > = guard right side
^
<x> --- normal
^
x>> --- situational example
Moreso with npcs than pcs (that I've found so far), if you keep moving around and hitting different specific areas, their will change their general defense layout which can be extremely advantageous for you to set up a directional combo (that's not to say you can't do the combo if their defense is up in that specific reinforced area, but you won't do as much damage). If you do a combo when an enemy's health is low, you have a chance of committing a fatality ( some blood goes on your screen and they get ripped apart).
Interface wise, somewhat counter-intuitive at first. All those previous games I've played had /commands you could do which AoC has abandoned. Once you get used to their interface, its more intuitive. I really enjoy the questing layout - when you talk to an npc, it zooms in on both of you, adds the black wide screen effect and you can select your responding choices numerically - it feels very RPG-ish.
Performance wise, I have a fairly decent computer and I'm able to run it at pretty good on dx9 settings (don't have vista + dx10 hasn't been "activated" yet).
I bought the game with my roommate and our other power gamer friend. My roommate hit 18 of less than 8 hours of game play, whereas for my power gamer friend, he's probably in his late 20's. Speaking of which, I'm only level 7 so I gotta go catch up. Hope some of this helps and if you need more info, I'd check out the community section of AoC. One last thing, though I haven't pvp'd much (on a full pvp server at the moment), they still need to fix where/how you respawn (normally when you die, you spawn at this magical pad - which are scattered throughout the zones) to tone down the ganking a bit. You're rewarded in pvp by getting abilities based on your pvp level so to say. I'll probably come back to this thread to post of any new developments and such.