Here is some useful information about using SSRS in SharePoint Integrated mode (included with SP2):

Installing the SharePoint Add-In

• If you plan to upgrade from a previous version of the add-in, you should uninstall the previous add-in then install the new one. After installing the new one, you will need to perform the RS configuration steps in SharePoint Central Administration again.
• If you have trouble with the install, take a look at the log files. In addition to the MSI install log, the Add-In also creates another log file named RS_SP_<number>.log. Both logs are found in the "<Drive>:\Documents and Settings\<User_Name>\Local Settings\Temp" folder.
• There is a known issue with the naming ReportServer.<culture>.resx files that are install as part of CTP3 in each SharePoint web sites' App_GlobalResources folder. After installing CTP3 this issue manifests itself as the following errors when you try to access any SharePoint web site:

Server Error in '/' Application.
Description: An application error occurred on the server. The current custom error settings for this application prevent the details of the application error from being viewed. 

To solve this, check the following in IIS Manager for each SharePoint web site:

• Explore into <Web site>\App_GlobalResources
• Do you see any Reportserver.<culture>.resx files (where culture is a string like EN / FR/ CS etc.)?
• If yes, then delete all Reportserver.<culture>.resx except for ReportServer.resx file. 

Deploying Reports to Report Server that is in SharePoint Mode

• Use the updated Report Designer that ships with SQL 2005 SP2 CTP.
• Deployment paths need to change for deploying to a SharePoint Document Library with settings something like this:

TargetDataSourceFolder: http://<MyServer>/<mySharePointsite>/<my_DataSource_Folder>/
TargetReportFolder:   http://<MyServer>/<mySharePointsite>/<my_Report_Folder>/
TargetServerURL: http://<MyServer>/<mySharePointsite>/

• If you see a login screen when deploying reports, inspect the web.config fle of the SharePoint web site for the following entry: 

<location path="_vti_bin/ReportServer/ReportServiceAuthentication.asmx">
    <system.web>
      <authorization>
        <allow users="*" />
      </authorization>
    </system.web>
  </location>

Make sure there is only one such entry in the web.config file. Delete any duplicates. Next retry deploying. This is a known issue in the CTP release that we are fixing for RTM.