HI,
It really depends on your use case and if you would like also to integrate non-SAP sources or not.
Have a look in this blog about real-time replication into BW with SLT: http://scn.sap.com/docs/DOC-40467
So I think you cannot give a statment - SLT is good/bad for BW. It is more about - it fits to my use case or not.
Best,
Tobias