That's not always a bad thing, however.
The base in the middle sports two plasma turrets on the underside (it floats in the air), and a force-fielded bunker on top of the platform. The walls are No-Team forcefields, so you can't get in that way, but the "doors" allow anyone through, and they don't slow you down at all. (Thus, they merely stop live fire from getting through) I found that once a team had control of this, with two heavies they could defend forever. I threw myself time and time again at it, only to be wasted on the way in, or die by the plasma turrets trying to get up. The few times I reached the platform.. the Heavies chased me around in a circle until they caught up to me with a mortar.. not fun. The best strategy I could think of was to fly quick through the opening in the forcefields and hit the switch.. then quick, jump on an inventory station, switch to heavy armor, and take out any spider-clamps that they'd set up before you.. and then try to hold on to control yourself.
Each base is "across the water" (by this I mean, across the lava) from the center capturable island, and the only way over is a long, narrow forcefield bridge. Again, if your enemy holds the center, they can spam you on your way in... missiles if you fly, and mortars if you walk. It can make for some seriously hard going.
The bases are the huge ones from Caldera. I had trouble finding my way around for the longest time, but that's because I have rarely even played on the bases before. The flag is in a rather hard-to-get-to spot; in fact, I would say it's impossible to get to, if a Defense has set up mines/turret network. At that point, you need a juggernaught to get in and soften things up.. but that, again, requires you to capture the center, or the Heavy Brigade will never make it.
Playability is a little low because of the supremacy of whoever has the center, and for the difficulty to even reach the enemy base, much less get to the flag. Attention to detail is very nice.. organics look at home, and the bridges seem to fit in, somehow. In addition, the lava is placed at such a height that it will burn you for carelesness.. but playing sane shouldn't get you in trouble.
Balance is given both to Defense, (who have a comparably easy job) and to whomever holds the Center; as I said, trying to take back the objective can be frustrating in the least.
Item Placement seems to be just right; the turrets have nice views of the terrain, and the inventories are all placed properly. The trees and bridges are lined up just so, and I can tell a lot of time was put into building the forcefields at the center.
Mechanics takes a slight hit because of two issues I found. First, you can change out at least one of the center turrets (it's a trick, but it can be done, even as high up as they are) with a different barrel. I put a mortar turret on, but I can't imagine the havoc an AA turret would cause. Second, once someone blows up those turrets (angry and upset offense seems to be prime canditates for that job) there is no physical way to repair them, thus negating much of the need for the center capturable, excepting as a sniping/spam platform. (which isn't all that small of an advantage)
With a lot of people, and perhaps with the addition of vehicles, this map would be even better, but there's really not much to knock even otherwise. The atmosphere was well done, and I did have fun staging attacks from the center. (yes, I finally did capture it, once..) Love lava? You'll like Marauder.