I miss this as well... the terrain used to be iconic to the game.
When you walked around, you would often find distinguished terrain... interesting hills, overhangs, and somewhat rarely flying islands. Since 1.7 there has been more biomes, but the terrain has almost looked smoothed out; less distinguished. There may even be less flat areas than before 1.7.
I would really like a pre-1.7 terrain mod or plugin. I know there's a preset called Neo-Beta on a thread, but to me it doesn't look fully like pre-1.7 terrain did (also just tried it out, oceans become green hilly areas... and thin strips of "beaches" go up and down hills).
Edit: You might be talking about beta 1.7.3. I started in Beta 1.8, which changed the terrain. There were still commonly floating islands and cliff overhangs, but it didn't quite look like the Gargamel and Glacier seeds. I miss the aspects of Beta 1.8 terrain, which existed all the way up to Minecraft 1.6.