I've been testing the JasperReport Server version 5.1 and I found this important bug:
First open a report that contains a table component or an table ad hoc. Second add a conditional formatting on column, for example value is greater than or equal to. And finally you can see how this new format is always applied on all rows.
I test in version 5.0 too and the output of function "equal" and "is not equal". These functions doesn't work.