There are TERRAIN_MASK_* constants within existing API which can be used for future analysis of this Uint8Array: distance transform, skeletonization, convolution with CostMatrices, transferring to WASM etc. IMHO, terrain data acquiring and transferring is pretty expensive now to try some advanced path/map techniques.

const room = Game.rooms[Object.keys(Game.rooms)[0]];
let t = 0;

t = Game.cpu.getUsed();
const arr = Game.map.getTerrainOfRoom(room);
t = Game.cpu.getUsed() - t;
console.log(`getTerrainOfRoom   = ${t.toFixed(6)} CPU`);

t = Game.cpu.getUsed();
const own = new Uint8Array(2500);
for(let i = 0; i < 50; ++i)
    for(let j = 0; j < 50; ++j)
        own[i + 50*j] = Game.map.getTerrainAt(i, j, room.name).charCodeAt(0);
t = Game.cpu.getUsed() - t;
console.log(`getTerrainAt 2500x = ${t.toFixed(6)} CPU`);

Typical performance tests:

[5:42:29 PM]getTerrainAt 2500x = 0.988422 CPU
[5:42:30 PM]getTerrainOfRoom   = 0.015738 CPU

Need reply to ensure there aren't security underwater rocks here (constructor or accessors rewriting?) Now I'm investigating it as well.

Pull request: https://github.com/screeps/engine/pull/83

NOTE: there is a typo inside function (.roomName instead of .name if argument is a Room object), it'll be fixed before merging.