There is no need to install Report Builder on every machine.You can configure to launch it from the browser. See:
http://msdn.microsoft.com/en-us/library/ms365173.aspxReport Builder is not the only ad hoc tool for Reporting Services. Because RDL format is public you can consider third party products such as Pebble Reports (
http://www.pebblereports.com ) While Pebble Reports can't be launched from the web browser, it too doesn't need to be installed on every machine. Users can start it from a network share.