It has been around long enough that any challenges you encounter can easily be found with a Google search. For the same reason (i.e., it has been around for a while), you can also find email automation software that works with Crystal to automate reports. I am satisfied with all the emailing options.
Long, complex, crosstab reports, which are nearly impossible! I have to think up crafty ways to enter the SQL, so I can get the data to appear. For the sake of data integrity, the base of all reports should be the raw data that the report pulls from, then do the counting, summing, etc. with that raw data. With Crystal, it is nearly impossible to work with the raw, row-by-row data.
Crystal is very limited when it comes to fancy graphs. If you want that, check out software that uses D3. Otherwise, Crystal is great, because it has been around for so long, you can get past any challenge fairly easily.