>GUID is good, but it have 32 bytes length compare to the integer (4 bytes). For large tables this is significant slow down and extra data.

Vlad,
GUIDs can be implemented under SQL Server 7/2000 as a UniqueIdentifier data type. As such, they are a 16 byte integer (not 32) so there is really no significant performance hit using them in large tables. If they are implemented as a CHAR type, then I agree that there is a performance hit.