I've been playing around with seeds for the last few hours and I've found some interesting tendances in the new worlds created with 1.3..
-LOTS of above ground lava pools now. In the 50+ worlds I created tonight, I found surface lava in 40 of them within a minute walk from my spawn. And they're usually a few blocks away from water. Instant Obsidian close to your spawn
-LOTS of above ground iron and coal (even more coal than usual)
-It seems that within a short distance (a 1 min walk) in any direction is access to EVERYTHING on the surface: caves, forest biomes, snow biomes, gravel, lava, sand, dirt, rock, clay
-OMG the clay.. In the '4chan' seed I loaded up my entire hotbar with clay digging by hand before noon in game (yes, that's 640 clay!)
Anyone else notice the 'supercharged' resource spawns?
The terrain generator has not changed in 1.3. The evidence for this is old seed numbers for previous worlds in beta still work and generate the same terrain as they used to. If the terrain generator had changed, the old worlds wouldn't be reproduce able with a seed number anymore.