MMOs borrowing from each other or not, Warhammer has the done the worst job of it by far. They have almost the exact same UI ffs. Party frames, minimap, and action bars are all in the same place. I've seen more creative UIs from the custom ones on WoW than that shit.
Not to mention that, like MAF said, the "RvR" (because PvP isn't cool enough they had to "borrow" this one from DAOC) looked awful.
Arena is reaching a level of complexity that is astounding for a video game that was originally meant to be geared entirely towards PvE. Of course, people still cry about counter comping and balance issues (BAWWWWW MY TEAM SETUP LOSES TO X TEAM SETUP EVERY TIME IMBA IMBA IMBA), but with this last patch it's actually probably the most balanced it's been in some time. And Blizzard has been quoted saying it will get better with WotLK. Rogues, Warlocks, and healers can roflstomp close to everyone 1v1 when specced/played right, but duels mean very little anyway.
Battlegrounds on the other hand are /snore. They haven't been the same since TBC and the new honor system. I cry a lot about casual players, and they do sometimes ruin battlegrounds at 70.
spoiler (click to show/hide)
WHY THE FUCK ARE YOU IN THE MIDDLE OF WARSONG FARMING HKS THAT DRUID JUST STROLLED BY WITH FLAG AND CAPPED WHILE YOU ALL SAT THERE WITH YOUR THUMBS UP YOUR ASS GODDAMN KEYBOARD TURNING distinguished mentally-challenged fellows DELETE YOUR CHARACTERS etc
Still, if it bothers me that much I should avoid them. So I do.
World PvP hasn't been alive since preBC either.
Willco: That is a relatively new thing. They've had tournament in the past, but this is the first time they've had a completely separate server for an Arena tournament. It's a great idea that should really be expanded upon in all honesty. Raiders have long been calling for a separation of servers between PvP and PvE so certain talent changes made for a specific aspect of the game don't cause balance issues with it's other half which is becoming a big problem. Unfortunately Blizzard feels the opposite. They have hard-on for the all-in-one package. The Tournament server is probably the most fun I've had with WoW in ages.
Shamless plug of me dueling some of the best people on the TTR~
http://media.putfile.com/ttr-duels