nope Only three of the five classes were playable in PvP, but they were sufficiently powered-up with numerous skills. I tried all three and while I think I had the most success with the Wizard, the Barbarian and Witch Doctor both had effective abilities and combat roles.
If Blizzard can balance this PvP, I could see it easily becoming an eSport. The matches are extremely intense and require tight coordination to succeed. It quickly led to taunting and cheering as we all figured out the game. The arena was square-shaped and full of pillars and barriers for cover. In the middle of the round, four health orbs will spawn in the center providing the only healing available to players.
There is some crowd control, but each class has an ability--with a long cooldown--that will break any roots, snares, and other effects. Additionally, each class has an ability that helps them move quickly around the map be it teleporting or sprinting. The spells at my team's dispel worked well together and we could easily kill opponents if we caught them unaware in a stun.
That isn't to say that a single player cannot defeat multiple opponents with careful skill use. Faced with a one-versus-three situation—I was the one—I used the Wizard's spells to defeat all three opponents. I would teleport around the map, breaking crowd control with my damage shield, and whittling down my opponents by placing magic-shooting hydras and landing lucky meteors. I also used my slowing field to slow down advancing enemies to give my meteors time to fall. Finally, the Wizard gets a focused beam attack that gets stronger over time. We immediately started calling it the "Void Ray" attack.
It sort of felt like World of Warcraft mixed with something like Guild Wars, albeit played in the classic Diablo isomeric perspective. I'm not sure how gear will factor into the arena as it makes balancing extremely difficult, but we were not able to customize our gear at the show.
Though there was no limit to the amount of rounds we played, it is likely that matches will be conducted in standard best X out of Y formats. Blizzard will offer matchmaking, rankings, and ladders for Arena PvP.
If you have any additional questions about Arena PvP or the spells of the Barbarian and Witch Doctor, please let me know in the comments.