Loop in get_metadata changed to:

if file_data['format'] == 'VBR MP3':
new_file = {
'title' : file_data['title'],
'download_filename' : file_data['name'],
'file_extension' : '.mp3',
}
try:
new_file['local_filename'] = "%s. %s%s" % (file_data['track'], file_data['title'], new_file['file_extension'])
except KeyError:
new_file['local_filename'] = file_data['title'] + new_file['file_extension']
new_metadata['files'].append(new_file)

Add the following code to ensure filenames are valid on windows:

isWindows = os.name == "nt"
def windowsFileNameSanitizer(filename):
#removes invalid windows filename characters
invalidChars = '[<>:"/|?*]'
return re.sub(invalidChars, '', filename)

Then in download, the main loop is changed to:
for i, file_data in enumerate(metadata['files']):
local_filename = file_data['local_filename']
if (isWindows):
local_filename = windowsFileNameSanitizer(local_filename)
local_filename = "%s/%s" % (metadata['local_download_dir'], local_filename)
print "[..] Downloading %s (%i/%i)..." % (local_filename, i+1, file_count)
urlretrieve(metadata['download_base']+file_data['download_filename'], local_filename)

if (not os.path.isdir(metadata['local_download_dir'])):
os.mkdir(metadata['local_download_dir'])
else:
print "[..] Using previously created directory: " + metadata['local_download_dir']