The maximum number of concurrent users that can view reports depends on the complexity of the reports (e.g. number and complexity of the formulas, number of summary fields, number of records fetched from the database, …) and on the server performance.
i-net Clear Reports can render approx. 3000 database objects per second on an 2400 MHZ system. A database object is a single value. The count is the product of columns and rows.