I have spent some time reviewing the latest iteration of ArcGIS Experience and I think it is a fantastic development in the "WebApp Builder space" enabling a kind of hybrid Enterprise Site and WAB experience for users. It is much easier to customise (e.g. adding home-grown svg's and the like), page design (much less restriction on page design), cross-hardware design (in built emulators) and incorporating arcade into widgets like Filter will be useful to use.
One notable exception missing is any sort of charting widget...I hope this is in the timeline but can ESRI comment on the inclusion of charts (like those available in Ops. Dashboard and the WAB Infographic widget)?
Also when in the development timeline will Experience be released for the Enterprise?