[Spritzo]

Anyone know if/how the increased map height will affect the Nether?

The Nether will be unaffected. You will be able to build to 256 but bedrock still starts around 120 and goes to 128. So the Nether won't technically be any taller. Tested this on a new creative map with the newest snapshot

Also, Redstone Lamps (lanterns) will require Glowstone blocks to be crafted.

[Bonejunky]

Anyone know if/how the increased map height will affect the Nether?

The Nether will be unaffected. You will be able to build to 256 but bedrock still starts around 120 and goes to 128. So the Nether won't technically be any taller. Tested this on a new creative map with the newest snapshot

Also, Redstone Lamps (lanterns) will require Glowstone blocks to be crafted.

Redstone lamps use glowstone? Well that sucks.

[Spritzo]

Couple quick bug updates for 12w07b:

NO caves are being generated, only lava pools, water pools, and dungeons.
NO End Stone is being generated in The End.
Birch Trees aren't being generated.
Huge Mushrooms aren't being generated.
NPC Village homes tend to appear partially underground more often than before.
Since The Nether reaches 256 but bedrock starts at 120, mobs tend to spawn on top of the bedrock. The mob cap is reached much more quickly because there is more flat land for the mobs to spawn on. And when mobs spawn up top, they don't spawn down below in the actual Nether.
tl;dr, less mobs are appearing in the "actual" Nether, oh, and mushrooms are spawning up there too.