What's the fastest way to retrieve a table's row count in SQL Compact 3.0 and 3.5? Use the sp_show_statistics stored procedure! Pass your table name as the first parameter (the second is optional) and you will get back a few statistics about the table and its indexes, so more than one row might be returned. The row count is on the ROWS column (ordinal 3), an unsigned 32-bit integer.
Note that this is not supported in versions 2.0 and earlier.