CiviCRM Community Forums (archive)

I'm a big fan of Crystal and provide report writing services for several clients, who only need to install the (free) report viewer to run reports and send results to PDF or Excel.  I haven't yet used it with CiviCRM (my own nonprofit is still so new there's no need yet), but I have pretty extensive experience using it to report on MS SQL databases.  I don't know anything about BIRT though, so I couldn't say how it compares to Crystal.  My thoughts:

Pros:
-Intuitive interface, drag and drop placement of fields and text.
-Grouping is simple, including nested groups.  For example, break down all constituents by state, then city.  Group functions change by data type, so you can do different things with numbers, strings and dates.  There's a cool one for dates to group by year/month/day/hour/minute.  Easy enough that you don't need to understand the GROUP BY clause when writing the SQL.
-Easy summary features to count, sum, average, etc, by group, including nested groups with option for a grand total.  For example, memberships broken down by type and pay method, subtotaled per type with a grand total.
-Web interface available.  My experience on the design side of crystal web is limited, but the end-user side is as easy as MS SQL Reporting Service.
-Prompt for parameters to do your filtering and calculations on the data fetching side or the report processing side, so you don't have to have a mastery of SQL to do cool stuff.
-Subreports.  You can create a main report and "import" multiple subreports, so you will find yourself making a handful of frequently used reports and reusing them without reinventing the wheel each time.
-Graphing data is also relatively simple.

Cons:
-Expensive, several hundred dollars.
-Closed source.
-To do advanced reporting, you must understand your data structure and build your own data source.  It can be an ad hoc query off the db, a view or a stored procedure.  Heck, it can be a spreadsheet.

Hope this helps!