Many companies will want more reporting options that are currently not available in OpenERP. Like many other ERP systems, companies will typically utilize and integrate alternative reporting platforms. Here are a few that are popular in the OpenERP community.
Jaspersoft offers a variety of both open source and licensed reporting solutions. There is a report server as well as a very nice graphical report editor available.
You can download the community edition of JasperReports Server from http://community.jaspersoft.com/project/jasperreports-server.
The server software provides report access and processing. To design reports graphically, you will need to download the iReport Designer for the operating system of your choice from http://community.jaspersoft.com/project/ireport-designer.
Pentaho, also known as Kettle, is a very useful tool for data translations and for reporting out to Excel or other formats. It doesn't provide the extensive reporting tools of Jasper, but is very robust for integrating OpenERP with other systems and creating automated data exports. Depending on your needs, Pentaho may fit your needs. You can get this from http://kettle.pentaho.com/.
Another popular reporting option that integrates well with OpenERP is Aeroo Reports for OpenERP. This solution doesn't have the robust reporting ability of Jasper, but integrates better with the OpenERP framework. It is an option that you may wish to consider if the built-in OpenERP reports do not meet all your needs. You can find a lot more in detail on Aeroo Reports at https://launchpad.net/aeroo.