I especially like how LibreOffice handles some things better than MS office, but then I am a power user. (These are issues in Excel 2010)
Specifically, one thing I can think of off the top of my head, the Control + End key combo takes you to the cell that intersects the last row and column of the sheet in both Excel and Calc (This is highly efficient way of highlighting from a specific point to the end of the worksheet). In Calc, it takes you to the intersection of the current last row and cell. If you have thousands of rows of data, and then delete some, it will take you to the last row of the current data. But in Excel, it takes you to the intersection of the last row and column ever used in the sheet since it was created. If you delete some data, save, close and reopen the sheet, and press the Control + End, Excel will take you to the last row that ever had data even if the sheet is now thousands of rows shorter.
It drives me nuts because I have business users who use a template sheet to build data they want entered into our Oracle system. Even though they'll only have a few hundred rows of data, when select cell A2, then hit Control + End, I often end up thousands of rows away from where the data ends. Sure, I only have to hold Control+shift+up to get back to the current last row, but it's still the same lack of polish in Excel that most users think Calc has.
Another issue in Excel, If I update the format for a range of cells, from Scientific Notation to Text, because I pasted some shipping track numbers into a sheet and want it to show the complete number, it doesn't redisplay after changing the format from General to Text. You have to F2 followed by Enter for EVERY CELL to force Excel to show the correct formatting. That, or paste the values in then use the import wizard to paste in the text values. Or Paste, Set the format, then paste again. But for a low tech user, it just looks bad.