I recommend that,use php script to generate javascript code is not a good way,so Yii could spend less effort on Zii development.
For usage of dropdown list,sortable table,javascript can do it better(I know,Zii is also generate some javascripts).But Zii generate javascript is less intelligent.
The fact is that there are PHP programmers that does not know how to use javascript, jQuery, ajax… so those Zii widgets can come handy to create a usefull site…
Advanced programmers can always choose if to use a ready solution or implement a custom one…
Yes!Zii is a good solution for those php programmers that aren’t good at Javascript.Also Zii, I can choose or not,it is low weak-coupling.
In fact, my suggestion also means that,PHP programmers could spend some time learning javascript(See Sencha–Ext JS or Dojo)(Or let other javascript programmer do this if your team has one).
Please understand me,I am also a javascript programmer,generated javascript is always a nightmare(Of course,Zii generated javascript has been very good and clean).