It was brought to my attention that fedutil does not work anymore with IdSrv v1 metadata. And I can confirm that.
The reason for this bug is my recent change to the XmlWriter factory methods which have a different default behavior when it comes to encoding.
Since there were only 20 downloads so far – I fixed the bug in-place (shame on me). So when you are one of the early adopters and run into this problem – just re-download IdSrv ;)