This looks very useful and I’ll definitely be enabling it to experiment.
One thing I’d find useful is the ability to link a template field to a user custom field. For example, in a support category the first couple of questions usually asked by the support guys are “Model of equipment” and the associated “Web site URL”. With this template feature I can now ask for this info as ech new topic is created 
These two bits of info are also generally of interest to other users so they’re defined as custom user fields - which sometimes get filled in. If template fields could be populated from a linked custom user field (if it has a value in it) then for frequent flyers they can fill in their user fields and not have to fill in the template fields in every time. Occasional flyers can just fill in the template fields as and when they need support.
As a further suggestion, the icing on the cake would be for the link to work in reverse. If someone enters data onto the template that’s not in the linked custom user field then the custom field is updated when the topic is posted.