Do data scientists use Excel?
Most non-technical people often use Excel as a database replacement. I think that's wrong but tolerable. However, someone who is supposedly experienced in data analysis simply can not use Excel as his main tool (excluding the obvious task of looking at the data for the first time). That's because Excel was never intended for that kind of analysis and as a consequence of this, it is incredibly easy to make mistakes in Excel (that's not to say that it is not incredibly easy to make another type of mistakes when using other tools, but Excel aggravates the situation even more.)

To summarize what Excel doesn't have and is a must for any analysis:


Reproducibility. A data analysis needs to be reproducible.
Version control. Good for collaboration and also good for reproducibility. Instead of using xls, use csv (still very complex and has lots of edge cases, but csv parsers are fairly good nowadays.) 
Testing. If you don't have tests, your code is broken. If your code is broken, your analysis is worse than useless. 
Maintainability.
Accuracy. Numerical accuracy, accurate date parsing, among others are really lacking in Excel.


More resources:

European Spreadsheet Risks Interest Group - Horror Stories

You shouldn’t use a spreadsheet for important work (I mean it)

Microsoft's Excel Might Be The Most Dangerous Software On The Planet

Destroy Your Data Using Excel With This One Weird Trick!

Excel spreadsheets are hard to get right