This morning I decided to VPN into the domain via my iPhone (v1.1.1) at home. I put in my regular password and received a prompt that my password had expired and the option to change it. (On 10.4 the login would fail.)
After submitting a new password, I updated my Mail settings to match the new password, and everything has been working great -- no Windows required.
[robg adds: I can't confirm this one...if you can, please comment.]

