I started PvP about a week before the big Extreme thing and it was very fun, never had any problems, people were nice, teams were great.. then came something so painfuly ugly it would shater not only a mirror but chop it up into little peices as well...
During my PvP times (which by the way is awesome with good people) ive run into good groups, bad groups and.. well one man groups. After only like 3 weeks of PvP i finaly see why everyone hates PvP, not because of the PvP itself but because of the comunity (hmm just like PvE.. makes you think).. some annoything things i have run into sofar are:
Runners - when one person is left alive they will more than likely run for their lives, if they are a warrior/monk with sprint this can be a real problem...
Leavers - Let me put it this way " Little Timmy has joined that game" "Little Timmy has left the game"....
Quiters - Much like leavers these people leave.. only this time its beacuse they feel the match is over, more than often it has hardly started
Whiners - "REZ ME" "REZ ME".. 10 seconds later "omg n00bs" "Moron has left the game" 5 seconds later, congradulations you are the winner...
W/Mo - Need i say more?
Double monk combo - Most annoying team build ever... 2 monks, two W/Mo.. two words "nearly imposible"
Sore losers - "OMG WHAT N00BS, I CAN'T BELIEVE WE LOST"... yeah.. i can't believe you have not found the cap locks key yet..
Bragers - even if they are on my team i can not stand people who are like "omg owned" in chat so the other team can see it.. "gg" seems to make them angry enough so stick with that, at least it sounds like your trying to be nice.
Multi-targets - Ok ya I understand i was not attacking the same target as you.. but its kinda hard when you do it to 3 diffrent people...
Lack of original builds - Ok i agree random areans is a by chance team but when your against a team of 4 W/Mo you start to think if they payed Anet off or something...
However, i have seen some good things aswell such as:
People with honor - I don't mean to brag but half the time im the only person on my team with this, i don't run when im the last person alive and when my whole team leaves i stick around to chat it up with the other team, if it can get them a few extra faction points then they will be happy
Friendly people - Once again a once in a life time shot but some times i see people who don't say "omg biggest n00bs ever" after their team loses. Personaly when my team loses i normaly say "Remeber me as a hero!" just to try to lighten the mood of the other people smashing their heads over their keyboards.... (so if you see that you just beat me

)
Worthy foes - They don't run, they don't say "my team sucks", they don't leave because someone did not rez someone and they stick around til the end... basicly people who don't blame other people for their loss
Friendly losing team - Nothing is nicer than seeing the team that just lost wish you good luck in your next match..
Not so serious people - This is a game after all
Overall PvP is not that bad.. but some of the people you run into make you want to step on an ant so you can feel like a big man... err well maybe thats just me