Two lanes, one huge central battle area, two huge immortals: what's not to like?
The above video does a better job of explaining the new battleground than anything I (or anyone else other than Blizzard could produce, so watch that first.
Interesting right? What is most notable is the two different mercenaries camps that populate the battleground. Unlike bruiser camps from older maps, the shamans that constantly resurrect their fallen hounds demand player attention. If ignored, it appears that their potential to summon hounds is infinite, which can easily exhaust towers and friendly minions.
The new variant of siege camps also appear more deadly to a single hero attempting to stop the push, which immediately brings to mind Brightwing, or the equally squishy Falstad that usually enjoy the benefits of being able to efficiently split push.
All in all, the battleground reminds me of Haunted Mines, as the objectives forces all players to meet at a central location in order to battle for the largest mega boss that will push opposing lanes. Haunted Mines is known for being very snowball-ish and, depending on the strength of the immortals, this battleground might be as well.
Also, The Diablo 3 style loot and gold after a nexus is destroyed is a nice touch.