Well I am also investigating the pros and cons of placing SSIS on the DB server.

http://www.sqlservercentral.com/Forums/Topic1459119-391-1.aspx#bm1459772

I think most of the pro's of putting SSIS on the DB server have been mentioned.

- Less licensing costs

- Performance benefits: the packages run close to the data (less network traffic)

- Easier scheduling via SQL agent is also a pro.

Cons

- SSIS packages compete for resources with DB engine (however most load occurs on the DB server anyway)

- Some SSIS packages won't run correctly if DB server is not in a DMZ

The last one is a problem for us because some packages access external sites (like FTP).

I think I can workaround this to implement some generic FTP service running on a seperate application server in DMZ to download the FTP files and put it on the internal network.