The following usage reports are available:
Site usage report Site administrators, including administrators of the Shared Services Administration site, can view usage reporting for their site by clicking Site usage reports in theSite Administration section of the Site Settings page.
Site collection usage report Site collection administrators for most site collections can view usage reporting by clicking Site collection usage reports in the Site Collection Administrationsection of the Site Settings page.
Site collection usage summary Site collection administrators for the Shared Services Administration site and individuals with personal sites can view the Site Collection Usage Summary page by clicking Usage summary in the Site Collection Administration section of the Site Settings page.
The data in SpUsageWeb.aspx don’t match the data in the UsageDetails.aspx page.
The issue is fixed in the April’s Service Pack, which is going to be released. We are now testing the Service Pack and will update you once we finish the test.
If no exception, I will send you the Service Pack early next week. Then you can try and see if the issue can be fixed by the Service Pack.
The _layouts/usagedetails.aspx page is still available in SharePoint 2007, although there is no link to it in the site settings page.
If the Site Usage Report works properly, the data in the usagedetails.aspx should match the data in the SpUsageWeb.aspx.