Hey all,
I just submitted a couple WPMU patches (one for trunk and one for the 1.3 tag) porting the changes Ryan made in WP to address the cookie authentication and password salting issues that have been generating a lot of discussion lately.
See standard WP Trac ticket #5367 for details. [1]
See WPMU Ticket #528 for patches. [2]
[1] http://trac.wordpress.org/ticket/5367
[2] http://trac.mu.wordpress.org/ticket/528