In the MSDN walkthrough and examples on using XSL to create a custom rendering style for a custom field type, the sample XSL all use the field's name as the reference. This is a bit silly - since it means the users need to create the new fields with the exact same name.
While the option to create a custom rendering based on the field name is welcome and will be very useful (if for example I am deploying a column to a farm and I want it to have a unique rendering template), the articles do not explain how to create a XSL rendering template for a field type - regardless of what the fields created from that type are called.
The solution is simple. Lets say your field type is "MyFieldType", then instead of the following line that uses the title of an instance of the field ("my field type"): <xsl:template match="FieldRef[@Name = 'My Field Type']" mode="Text_body"> use the following line instead, which uses the type name of the field: <xsl:template match="FieldRef[@FieldType = 'MyFieldType']" mode="Text_body">