Way past time they got back to basics, got the core of the OS robust (could take a lot of lessons from RISC OS actually) including the core of the UI/shell, user friendly and decently customisable by the end user. Split updates out again so that security updates can be applied quicker and in a more streamlined fashion and users better able to manage feature updates at their leisure and end user having better control over drivers, etc. and I could go on.
Still don't know what they were thinking with file explorer either it is such a mess of ideas put in at different times by different people (I assume from the mishmash of approaches) - Windows 7's one is pretty close to spot on other than some bugs with refreshing contents and lack of the advanced file copy dialogues, etc. that were introduced in 8 onwards (some other features for working with multiple files wouldn't go amiss either such as advanced renaming of multiple files). For touch, etc. the left hand navigation pane could have an option to display large icons there for functions that could be either touched or dragged and dropped onto and an additional entry in the lists in the navigation pane containing a list of currently opened folders so you can drag and drop a file inside its own window into another location to copy, etc.
If they are going to go with the new style of Start Menu (which I like in theory) then there needs to be a higher level of customisation over icons and groups including proper group management features (even Windows 3 did this) as well as the information displayed on tiles, etc. with in a general sense a bit of utilising it like the home screen on a phone.
Then generally update the look of the OS or at least some additional customisation options so that it doesn't overall look like something the intern whipped up in mspaint on their lunch break. Sure 7's look is a bit dated now but most of the graphics look like they were professionally designed and fit together well and overall has a much sleeker presentation.