Hi, this script needs work! On OSX it tries to run this:
Running dd bs=1m if=2012-09-18-wheezy-raspbian/2012-09-18-wheezy-raspbian.img of=/dev/disk1...
Waitingdd: 2012-09-18-wheezy-raspbian/2012-09-18-wheezy-raspbian.img: No such file or directory
It can't find the file because ...raspbian.img is unzipped into the same level as ...raspbian.zip, not into a subdirectory. This may be something OSX does weird or maybe raspbian have changed the layout of their zip. In any case you should list the contents of the zip file and look for the largest .img file in it, then use that.
This can be fixed by making the following change on line 189.
path = file.replace(".zip", "") + '/' + os.path.basename(file).replace(".zip", ".img") #Thanks to Lewis Boon
path = os.path.basename(file).replace(".zip", ".img")
Looks like unzipping utility handles things slightly differently, depending on the OS.