I had been using the mc23 for a long time now, and have been listening to the version 25 for the past few days. I feel that the sq. at the frequency extremes has improved, specifically I perceive more low end extension and more airiness in the treble, or maybe it is just an expectation bias. Regardless this version of Jriver is sounding excellent, and as Nikhil mentioned the Gizmo remote has added another degree of flexibility to its already excellent UI. I am still running windows 7, looking to upgrade to 10 soon and hope there will be some further degree of improvement in SQ.
Cheers,
Sid