I think the escaping workaround should be documented in the glob and/or fnmatch docs.  This way users can simply do:

import glob
glob.glob("c:\abc\afolderwith[[]test]\*")

rather than

import glob
import fnmatch
glob.glob(fnmatch.escape("c:\abc\afolderwith[test]\") + "*")

The function might still be useful with patterns constructed programmatically, but I'm not sure how common the problem really is.