Workbench without DesignModeller is not worthwhile, in my opinion. DesignModeller is an analysis tool more than a CAD program; it has a lot of great functions which help the analyst clean up your geometry for modeling. For example, there are tools in DesignModeller specifically to help the analyst detect and remove slivers, chop up geometries for meshing, or create shell bodies.

If you're planning on doing your model manipulation in a CAD program outside of Ansys, I'd suggest that Workbench has only limited benefits over the traditional Ansys environment (Ansys APDL). I see the biggest advantage to Workbench as being the unified environment for working on models. Classic Ansys certainly has more functionality when it comes to more complex problems. APDL allows users access nonstandard element outputs, access results for subsets of nodes on the fly, and to parametrically adjust just about anything in your model for optimization purposes.

Of course, all of the extra functionality of the Classical Ansys interface comes at a cost: It has a somewhat steeper learning curve. A veteran analyst will tend to use the Ansys syntax to create useful, elegant, fast-solving models which answer critical design questions more quickly and effectively; however, it takes a while to pick up the user interface and to learn the Ansys Parametric Design Language. That's not to mention the time that it takes to learn different analysis techniques and which technique best represents the case at hand -- which is a software-independent skill.

Regardless of whether you get Ansys with DesignModeller or not, it's great software and I'm sure you'll be happy with it. Good luck.

//signed//
Christopher K. Hubley
Mechanical Engineer
Sunpower Incorporated
Athens, Ohio
--
http://engineeringliberty.wordpress.com

One important thing that I didn't mention: If you try and use Workbench without DesignModeler, you'll be unable to tell Ansys Workbench to share nodes across slices in your model... which is important for meshing (see VGLUE).

Current meshing technology isn't able to effectively break up complex geometries into regularly shaped bricks, so analysts often have to "cut-up" their models and glue them back together so that the mesher has an easier time with it. Brick meshes are much more efficient than tetrahedral elements (i.e. fewer elements are required to achieve similar levels of accuracy).

That's how I tend to use DesignModeler: to de-feature geometries, and chop them up, and glue them back together into "multibody parts". It's handy that Workbench provides a unified environment for this sort of thing. Version 13 actually does a pretty good job of it.

//signed//
Christopher K. Hubley
Mechanical Engineer
Sunpower Incorporated
Athens, Ohio
--
http://engineeringliberty.wordpress.com