The level editor is "FINALLY out on Steam!" McMillen rejoiced.
Technically, the editor is in beta release -- "and probably will be for a very long time," McMillen notes in a blog post -- so users may encounter "minor issues." Still, with the exception of boss battles and warp zones, the editor can be used to create "anything you see in game," and even package such torturous levels into a complete chapter of pain.
"So think of this as a thank you to all the awesome fans who sent us cool shit, nice emails and created amazing levels with devmode," the ever-irreverent McMillen concludes in his post, "if you bitched us out because the free level editor was delayed, you should probably not update your game and burn in hell."
McMillen added in his email that Super Meat World would be updated next week to add a few "missing" features and fix some bugs with the editor. "After that we will be closing the book on the PC version, porting SMB to Mac and swiftly moving on to game #2."