ECC and BW in the same system - Gotchas?

From the documents, and from the information from SAP, it appears that BW 3.5 can be installed into an ERP 2004 / ECC 500 system. Does anyone have any experience with this during the ECC 5 rampup?

I have a client that is considering this and would like to know of any gotchas before we hit them.

For instance the documents mention you need to tune the Oracle database with the parameter "star_transformation_enabled=true", which is normally used in a BW system. What impact, if any, will that have the ECC side of things?