CoV is an amazing expantion to an already amazing game.
First off let me say that in a world fild with bad mmos its hard to tell at first glance where the good MMOs are, I will start this out by saying CoX (CoX= Both City of Villians and Heroes) is a beacon of glory within an ever tainted market.
The game is a bit of a grind, not going to lie about that but it sets itself apart from its compotition. Sure WoW has flying mounts but CoX has had flying since launch... in all zones mind you.
Sure WoW and Dark Age of Camalot have RvR... so does CoX, and in a very player friendly way. RvR in CoX is built around brackets. There are 20s, 30s, 40s, and 50s zones... the best part is if your 50 you can still go into the 20 zone. They have a neat system that lowers your level making you equal to everyone on the feild... whats that only 10 sure jump into the fray because you'll be lev 20 when you enter (aside from the fact that your skills will be undeveloped compared to a 20+ toon, but hay its unlimited pvp!!)
RvR in CoX also has an interesting twist, within pvp zones you can do missions to attempt to weaken your foes this isn't always necessary to win but it helps when your out numbered.
Now moving onto the core gameplay you have to realise that sure you've got a sprawling city but most of the action happens inside the buildings, sewers, caves and other random locations. That is you'll spend most of your hunting/questing time in instanced mission areas which are all connected to massive open presistant zones. The graphics to this day hold up very well as Cryptic (and now NCsoft) has constantly added free updates to the game.
That brings up my next major topic, free updates. CoV is the ONLY expantion to this game but don't get me wrong the game has been expanded a ton, and for free! Not only have they added 2 major classes and numerous zones and raids but 2 more classes are on the way (the added classes are gained by maxing out a villian or hero its like SWG jedi back in the day but not over powered but more a privlage). It seems every 3-5 months you can expect some kind of major update to the game. Aside from classes the devs have added many power sets (this is like a flavor of a class) to the game sinc launch.
Continuing on customization is key in CoX. You've got it all, you can be a magic weilding super ninja, to a robotic death machine that can cloak itself and slice people up before the know whats happening. The point is if you can imagine it CoX for the most part can built it. I've actualy met a few people who have gone on to create minor comic books or storylines revolving around their toons, thats how much people get into it. My biggest issue from time to time is having to much customization, often I get lost in a sea of possability.
CoX also features a great reward system, you'll gain titles, temp powers, crafting objects, costume parts such as wings, jetpacks, and much more. As you level up you'll gain acces to auras and other neat cosmetic things that'll make your hero or villain truely stand out. The game also features a robust and highly developed veteran reward system which is NCsoft's way of saying "thanks", some of the high end rewards are realy nice wepons or powers (wepons are always a form of power).
To end it off if your sick of the many MMOs that have you activate an auto attack and click skills as you go then try out CoX. Its got a real time skill system, no auto attack at all so you have to be actualy ingaged and playing during combat. The game is one of the most face past MMOs I've played (aside from Auto Assualt... RIP) and if your a villain playing a MM (Mastermind) will have you commanding a small army of critters/bots/thugs/ninjas/or zombies