Looks like NAnt and NAntContrib have hit 0.85 RC1 status. I've been using an interim build of 0.85 for quite some time now in a production build script, and it's awesome. The support for functions in particular makes a lot of things a lot easier. I'd still like to see iteration over XML nodesets ala XSLT's for-each, but I'm not really complaining.
Check it out if you're still on 0.84.