I'm playing on a PvP Server off and on. It's fun, but it has issues that might turn many off.
-Balance is pretty bad.
-There isn't a reward (or penalty) system for open world pvp.
-The world is fairly small.
-The UI is very limited and quite literally the game is easier with a controller on a PC.
-The UI is VERY limited (worth stating twice)
-No system in place to keep sides close to even. At least a 4-1 ratio villains to heroes.
-All PvP gear is acquired via basically doing Arenas.
That all said, it is not particularly hard and there are a lot of new/bad players. I'm enjoying it now but can't see the PvP servers being populated very well in a few months when everyone who is just "trying it out" leaves. If you are ever going to try it at all... you better try it right now (IMHO).
Lot of flash, little substance... but sometimes that is good for a good time.
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Excess - hellscream