Its so much fun watching the WOW crew battling it out with pistols at 10 yards over which way is right, which class in imba, which profession is uber etc etc
If your new to the game, its worth picking a new server like Aerie Peak which is still growing, there will be pleanty of people at your level to quest with, and you have a chance to get into a good guild which isn't so advanced they won't even look at a level 60 without tier 1/2.
PVP is ok but expect ganking and a lot of it - Its a game and some people enjoy the whole gank/be ganked others don't. If it gets to the point where you're not playing for fun or playing is no longer fun then time to look again.
PVP is available in Battlegrounds anyway, which is a much more fun way of doing it.
If you can try all the classes to at least level 10 to get a brief idea of the way each one plays and what they offer and which you will enjoy. Here is a brief summary of a few clases i have experrienced. The strengths in the class depend on the player, some classes will beat others more easily in PVP but every class has its nemesis and forte - Each class is different and fulfills a different role. Each class has different stats, health, mana/energy/rage and armor, tanks take longer to kill than casters etc.
Warrior - Main Tank holding mob agro (good class always in demand, can be a bit tedious to play but can survive well)
Priest - Main Healer (good class can be played to either kill or heal, if you enjoy healing instead of fighting in groups its fun if not then its not and gets very tedious. In groups and dungeons as a preist you will be expected to heal not kill despite the fact in shaddow spec priests kill very effectively)
Mage - Ranged damage dealer and crowd control (good class, quick to level but lots of down time due to needing to refresh health and mana but again)
Rogue - Up close damage dealer (my favourite class for fun value as is very versatile, you can sneak about in stealth, kill mobs quickly etc) If your playing a rogue it takes a lot of skill to get it right as you can't take that much damage.
Druid - Hybrid class worth a slighlty longer explination (at the end of the day as a druid in a group the chances are you will be the healer or healer support and crowd control/AOE- Although in animal forms you can tank and do damage you wont replace the main class. However unlike a priest when your healing people and you pull agro you can shift into dire bear and take a few hits without dieing, where a priest probably would die, untill mobs are pulled off you)
Hunter - Ranged sustained damage - Every man and his gold farmer rolls a hunter, there are millions of them, some are bots grinding for gold and items, others are first time players, because, it is an easy class to play and level with minimal downtime. And then there are a few, very skilled hunters who can get the most out of the class. Hunters get a bad rep due to the sheer number of bots and inexperrienced people playing them. A good hunter makes this a very strong class, its just finding one thats the problem.
Warlock - Damage dealing, life stealing the list goes on. Its a good class to play, requires dedication and can die easily but is always in demand.
Paladin - Can't die can't kill - harsh but true, it takes a long time to kill a paladin as its basically a warrior crossed with a priest all the strengths few weaknesses, appart from the fact it takes ages to kill anything so levelling is long. Watching two similarly specced well played paladins duel is like watching a snooker match or test cricket, there will be a winner.............eventually.