It works fine in interactive mode, I mean the normal static mode. You can edit the preview size but that has it's own issues (I want it to actually look like a real screen), and it seems to affect quality (maybe through DPI), a high height preview decreases the quality of the preview.
If you look at a preview of an XML layout, you can scroll it just fine, and if you mouse over a Compose preview you can see the node outlines extending out of the viewport, but you can't actually scroll to them.