For those who hear an improvement in SQ with 1.8 - Congratulations !
For those who hear a deterioration in SQ with 1.8 - consider changing to a topology that separates the Output from the Core. Any change in SQ between versions of Roon is probably due to the computing load on the Core. Using a network device such as a Roon Ready endpoint or a network adaptor running Roon Bridge will provide some isolation from the Core.