If I may chime in, as I don't know where else to put this.

I am still seeing the same performance as the OP when I use extractall() with a password protected ZIP of size 287 MB (containing one compressed movie file of size 297 MB).

The total running time for extractall.py was
real    35m24.448s
user    34m52.423s
sys    0m1.448s

For a bash script using unzip -P the running time on the same file was

real	0m19.026s
user	0m8.359s
sys	0m0.414s

extractall.py loops over the contents of a directory using os.walk, identifies zip files by file extension and extracts a certain portion of the filename as password using a regex. If I leave the ZipFile.extractall part out of it and run it it takes 0.15 s.

This is with Python 2.7.1 and Python 3.1.2 on Mac OS X 10.6.4 on an 8-core MacPro with 16 GB of RAM. The file is read from an attached USB drive. Maybe that makes a difference. I wish I could tell you more.

This is just for the record. I don't expect this to be fixed.