Last week, the huge patch to improve XUL templates was checked in. After a few regressions were fixed, it should now be usable. Of course, you'll need a nightly build to try it out. But, some new features are available, such as support for better conditional checks and simple control over recursion. For more information about these feautures, see Template Features in 1.9

Soon, support for building templates using XML, Storage or other data will be available. I have some code for these about half written, although it needs updating a bit for more recent changes to the template builder. If you'd like to actually help implement these properly, you may wish to comment on the corresponding dependency of bug