Thank you for this question. I utilized Tableau before coming to Tableau 6 years ago. I found that the company I worked for had a culture of locking data access away to just a few people and gaining access to use tableau on those data sets was my challenge. Eventually, the organization adopted Tableau throughout the org and setup Tableau Server with server based data sources but those early days were rough and challenging.
As for desktop specific issues - my learning curve on desktop was helped a great deal when I started at Tableau. The one thing I failed to grasp for awhile was Table Calculations. I worked my way through examples but eventually it was the kind mind and words of Jonathan Drummey that showed me the ways of these magical calculations. Jonathan has written many helpful articles and guides to learning Table Calcs and many things Tableau on his site - drawingwithnumbers.artisart.org I suggest reading and using the Zen Master blogs in addition to all of the great online training - Learning | Tableau Software to get started. - Especially the series "Why is Tableau Doing That?" - These are a must for anyone trying to take their Tableau skills up a notch.
Users who still want crosstabs because they can't get their head around anything that doesn't look like excel.