For MutableTimes - I'm mainly focusing on the static content aspect of publishing. I'm going to look into rendering via XSL instead of the MT templating system, we'll see how that goes.
MovableType has done a nice job with their management interface and their WeblogPublisher.pm module. I really don't want to reinvent the wheel in that regard, but I do want to use XSL.
Thankfully there is a perl module for working with XSL:
http://linuxfocus.org/English/July2000/article156.shtml