What classes will thrive in this environment? As with all PvP, mobility is key. As mentioned, in this case, classes that can traverse water with impunity will have a significant advantage over those who must cross it conventionally. Teams will be tasked with sticking together through the numerous bottlenecks in the map, from bridges to uphill passages, so group buffs such as Path of Frost or Crusader Aura can miss a member or two along the way. It's not always wise to stick close together, either, as that's just as easily countered by AoE effects, such as a well-laid Frost Trap.
Hunters look to do excellently here, as the bottlenecks will be excellent places to drop traps. With the new Trap Launcher ability that allows them to deploy traps from a distance, hunters can use traps reactively instead of the typical preemptive method. Hunters can scout where groups are passing and unleash traps accordingly along one of the pathways. The higher ground of the Wildhammer Longhouse is conducive to sniping away at opponents, as well, and ranged classes enjoy a small advantage over melee classes in the sprawling area, as is expected for the battlegrounds.
Druids, the best flag carriers in the game, will continue to thrive in Twin Peaks. In fact, they get even more options here as they can employ Aquatic Form as a means to escape or hide and Cat Form to negate the fall damage from the Alliance base. Players who enjoy the shapeshifting aspect of druids will employ it well in this map, as long as they can manage the mana. I'm personally not digging the troll druid forms, but I'm quite likely to roll one, anyway, if only to enjoy the class in the Twin Peaks environment. Balance druids can knock back enemies in plenty of spots, too, and the new abilities Stampeding Roar and Wild Mushroom are perfect here.
Likewise, shaman get better in this map because they can utilize Water Walking in addition to Ghost Wolf. As with hunters, they also have more effective spots to drop Earthbind Totem as opposed to, say, Warsong Gulch. A well-timed Earthbind Totem dropped on top of the bridge in the middle of the map will slow down a group of mounted pursuers, one of whom will probably dismount just to destroy the totem. As mentioned, Thunderstorm will also see great use in this map. Overall, a great battleground for shaman on various levels.
Warlocks should have a lot of fun with Demonic Circle, and some forethought will create problems for enemies the same way that it causes consternation in Warsong Gulch now. Clever warlocks place Demonic Circles on the upper floor overlooking the flag room, allowing them quick escape after nabbing the flag. In Twin Peaks, there'll be a lot more options, and warlocks can use it as a means to quickly traverse the different levels on both ends, particularly the Alliance base. In conjunction with Soul Burn, warlocks can get that extra burst of speed after teleporting, making pursuit extremely difficult. We won't even discuss how much fun warlocks can have just applying DoTs on everyone in a battleground.
Mages aren't left out on the fun, either. I've sung praises about the Wall of Fog ability that mages will receive in Cataclysm, and like hunters and shaman, mages have plenty of spots to detonate it. Rogues' Smoke Bomb won't have the same utility, but will be great fun to unleash in the flag room or even just to confuse pursuers. If Heroic Leap makes it through the beta this time around, even warriors will get an improved experience in this battleground provided the spell's pathing allows them to circumvent traditional movement barriers such as elevation. In the past years, I would've doubted it, but the developers are approaching the game with a new perspective, so I wouldn't rule it out.
Paladins don't get anything particularly exciting in terms of group or battleground PvP aside from new group heal utility, but that lends itself well to any battleground. Their notable lack of mobility will continue to hound them in this map, but protection paladins should naturally do well as carriers. Death knights don't get anything, either, but at least they have Path of Frost to play with. Priests get their Leap of Faith, which I mentioned last week and makes them the ideal healers for the flag carrier, especially in an interesting map such as this one.
Overall, almost all classes will have an improved experience in Twin Peaks, with the map pushing players to use their abilities creatively. Two graveyards on each side will eliminate graveyard camping and give groups who don't have as much combat expertise as the opposing team a fair chance at winning the game through completing the objective. The asymmetry is such that strategies per side will vary slightly, but not so much that it should cause outcries of imbalance. Think of it as Warsong Gulch 2.0, new and improved. As exciting as the map will be to test out in beta, it will be crazy fun when it's finally unleashed to an 11-million-player community. The clock is ticking, and I can hardly wait.