use JIRA Core or JIRA Software
and miss some Excel-specific functions from them like
an Excel-like view of their issues
an Excel-like way of creating and editing issues
importing and exporting their issues from/to MS Excel
copy-paste (also to/from MS Excel/Notepad)
an Excel-like way of filtering and sorting issues (without JQL knowledge)
seeing the Average/Count/Sum of the selected cells
column renaming
column freezing
tab cloring
row flagging
So, JExcel is for anyone who has to deal with issues in JIRA.
If you like our features, don't hesitate to use them!
And if you don't... it makes us sad, so help the Earth be a happier place and let us know why you don't like it.