In case I raised too high expectations: It’ll take a while. All other available view renderers are backed by PHP in some way. XSL/T is a complete language on its own. The biggest problem atm is proper serialization of models.
BTW: I do not intend to write a renderer just for XHTML. I’ve got a general purpose renderer in mind that’ll allow you to produce XHTML, XSL:FO, Atom, RSS, WML, …
Dunno, I’m making rapid progress. I can already deliver simple views. I’ve found a way to call Yii::app()->* from within the XSL (not implemented it, though) and I’m getting better and better at passing entire models and their relations as parameters.
Well, I ended up with a solution that’s working good enough for me but is not nearly good enough for GA. One unsurpassable problem I’ve faced was the inability to call any of the Yii::app()->* service methods stemming from a limitation of PHP’s XSL processor.