Biggest issue I have with them is that they don't support Drag and Drop.
For example with Groove Music and Movie player, I can't drag and drop a folder with music or videos to them to add to a playlist. To me this is a step backwards.
Other than that I do believe they improved a lot since windows 8 and they are much more functional.
Just to clarify, not having Drag and Drop is not an API limitation (see [1]). Rather, they haven't implemented it yet in every place you'd expect to see it.
For example with Groove Music and Movie player, I can't drag and drop a folder with music or videos to them to add to a playlist. To me this is a step backwards.
Other than that I do believe they improved a lot since windows 8 and they are much more functional.