Here's the welcome page with a small accessibility icon:
The new interface has a lot in common with the new desktop home screens for Docs, Slides and Sheets. All of them use the new Material Design.
Here's the contextual menu:
When you click a file, it's selected and the info pane shows more information about the file. There are no more checkboxes: click to select, double click to open.
There's an updated "new" button that lets you upload files and files, but also create new documents.
You can now resize the sidebar:
It's easier to select files: click and drag your mouse over several files or press Shift to select a range of files or press Ctrl to select non-consecutive files.