We need the ability to calculate a single workbook when multiple workbooks are open.
When working with multiple large slow workbooks which are often not even linked together (think multiple versions of the same workbook or a large mostly static workbook being referenced by a smaller rapidly changing workbook) you want to make changes and recalculate without globally recalculating all open workbooks.
This should be implemented as
a) New calculation setting (persistent) - Calculate Active Workbook Only - works for Automatic and Manual F9, but Ctrl/Alt/F9 would full calculate all open workbooks regardless of the setting.
Automatic Calc in Active workbook only would recalc the active workbook whenever the active workbook changed.
b) VBA Workbook.Calculate would only calculate the referenced workbook.

This will also become a critical need when handling multiple workbooks on non-workstation endpoints

There is a bug with the processor usage, which extends up to 99% in some special situations.
Since the latest version of the semi-annual channel, there is a new bug, which is also in the latest version of monthly channel.
When you are opening a new excel sheet and copy one or more cells then you can start playing a little "processor-game". On the bottom there is a slide control, when you push it to the verry left (over the table sheets) the processor usage will grow up to 99%, when pushing it back to the right, the usage decreases. You can slide it as long as you want.

A Table has a lot more functionality than a List. Although there are 6 different ways of converting a List into a Table, Excel users find it easy to do that with a shortcut. Surprisingly there are 2 shortcuts performing the same exact task:
CTRL + T (T stands for Table) or CTRL + L (L stands for List)
Why should we reserve 2 shortcuts for the same action? let's keep only the relatively new one CTRL + T (users are familiar with this one)
While Assign the older shortcut CTRL + L to copying to the left (L stands for Left) maintaining the same logical association:
CTRL + D >> To copy Down (D stands for Down)
CTRL + R >> Copy To The Right (R stands for Right)
CTRL + L >> To copy to the Left (L stands for Left)

My customers reported me that my product (Excel Addin) becomes slower after they updated Excel from 2010 to 2016.
By analyzing the problem it turned out that main reason of the slow performance is 'ClearContents'.
I setup two same hardware condition machine. I installed Win10 into them. Then I installed Excel 2010 on the machine A.
And I installed Excel 2016 on the machine B.
By using the following code, I measured the time to ClearContens.

It takes 2859 ms on Excel2010 (A) . It takes 9719 ms on Excel2016 (B).

Generally thinking , a customer will expect faser performance for a new version. But the opposite situation occured here.

[Code]

Private Declare Function GetTickCount Lib "kernel32" () As Long

Sub Main()

 Debug.Print "Excel version : " & Application.Version

 Dim n As Long

 n = GetTickCount


 For y = 1 To 500

 For x = 1 To 100

         Cells(y, x).ClearContents

     Next

 Next

 Debug.Print GetTickCount - n & " millisec"

End Sub

There are calculations so large and long that Excel is unresponsive until they are done. It will say something like "Book1 - Excel (Not Responding)" in the title bar. The GUI will not update and will fade if you try to click in it with your "hourglass" cursor.

If I didn't know any better (and I used to not know any better), I would assume that Excel was frozen and just kill the process and lose all of my saved work. But it isn't frozen. It's just taking a very long time. This should be made clear to the user but isn't.

For an example of this, fill columns A and B with all 1s. Fill column C with SUMIF(A:A,1,B:B). Excel should appear frozen for a few minutes.

There is No synchronization between the Filter command on the Table Design Tab and the similar command on the Data Tab. So if you apply a Filter from the Data Tab then clear it, the corresponding Filter command on the Table Design is inactive. On the Other hand, if you insert a Slicer from the Table Design Tab ► it inactivates the Filtering commands on the Data Tab. Filter on all tabs should synchronize together as well as with the Slicer.
Looking at the distribution of commands on the Table design Tab, I would prefer removing the Filter command from the Style options group (it has nothing to do with formatting) and rather group it with the Slicer button in the Tools group. to avoid any confusion I would also move the 6 options affecting the styles, to the right side of the Styles gallery. Look at the before and after design.