You probably noticed already that minecraft 1.0.0 is full of bugs!
I know that they will be fixed (hope so) but come on, i never saw that much bugs in minecraft!
1.0.0 came with lots of new stuff and lots of new bugs, like:

The ice has every 10 blocks or something like that strange stripes;
There are strongholds destroyed by mine shafts;
Trees that grow between different biomes have different kinds of leaves (i have find one that has 4 different kinds of leaves on it);
Lots of NPCs are destroyed, for example a house that is underground (only the roof is visible);
If a river is flowing through a swamp then there are 2 kinds of water (the green and blue);
In old worlds where is winter it doesn't snow but it rains;
The terrain in some places looks terrible, for example, stone fields on the surface (like in the picture);
Placing a block next to double doors cause them to force open;
Sugar cane can be placed underwater;
and there is even more buggy stuff...

If you notice any more bugs please write it in a comment so I can put it in this list.

I don't say that 1.0.0 is bad, i like it but the terrain generation could be better and some bugs really need to be fixed. I know that these bugs will be fixed but i think that 1.0.0 is released to early.