V1.2 of the Oblivion Construction Set can now be downloaded from the Official Elder Scrolls site.

But, before you download it, there are a few things you should know:

• You have to use the 1.2 patch for Oblivion as well, if you want to use this new version.
  
• When a mod is edited with the 1.2 version of the Construction Set, it can no longer be edited with the original version of Oblivion and the Construction Set.
  

So if you are working on a project with a group, you'll have to make sure you are all using the same version.
But I think (correct me if I'm wrong) you can still play the updated plugin without having to use the latest official patch. (Of course, downloading the latest official patch is always recommended)

Now, for the changes... I was expecting a large change log about half the size of the game's patch. I was wrong. Not many bugs were fixed. But there are new features.

The new feature:

'Spell checking functionality'
From all the features the community has suggested, I'm sure this one is what we've all been waiting for. Right.

Even though that's the only feature mentioned at the New Features section, at the Bug Fixes section it has a few more. Just take a look at the Patch Notes.