I have been using ERWIN extensively as well and I have found it being used by many large companies so it is a good tool to learn.   It is much simpler to use ERWIN to make multi table changes than to use Enterprise Manager and of course modelling before creating reduces costs due to fewer problems down the road.   While ERWIN works fairly well for design and generation of the entire schema I would agree that for the price the ability to generate correct change scripts is poor.  To the point where I have generated the model to a blank database then used a SQL compare tool like Red-Gate's SQL Compare to generate the change scripts.