I upgraded last night to Movable Type version 4.2 RC1 (a beta). Living bold!
I also added three OpenID plugins and turned on some internal login features.
This is the good news: Users can now log to make comments with their AOL/AIM screen name or their Yahoo, Wordpress, Vox, and LiveJournal user ids in addition to a "regular" OpenID login, Typekey login, or even anonymously. That should make commenting a whole lot easier.
The Yahoo and Wordpress plugins were written by MT developer Byrne Reese and the AOL plugin was written by Minh Nguyen. The Vox and LiveJournal logins are native to MT 4.x, but I hadn't turned those on previously.
I only ran into one glitch. I couldn't see my blog preferences menu (which is bad). I turned in a bug report and decided to sleep on it. This morning I went into MT's beta forums and got the answer in four minutes! User dug said disabling the iPhone/iTouch interface plug in fixed that for me. It did for me, too! Hopefully, that plugin will be upgraded.
A number of new things and performance improvements are in version 4.2 RC1, if you are interested.