Some of the new blogs that have been released recently (for instance, Jake Humphrey’s new blog on the F1 section of the site) had a new look that didn’t match the existing columns.
Now it seems as though the other blogs will be moved over to the new design gradually, with the internet blog one of the first to move.
The new look is much cleaner and matches the rest of the site, and it makes the different elements of each blog (links, subscription options, photos) much easier to find.
Update: There’s a nice side by side comparison on the Editors blog. From the tone of the comments, it seems as though the new look isn’t popular, but change always takes time to get used to.