I cannot give performance comparisons of Warewolf vs MVC and Entity Framework.

Currently, Warewolf is intended to augment your existing development stack not replace it.
We have focused on enabling simple and quick SOA by allowing DLLs, Web services and Stored Procedures to be quickly exposed and orchestrated in Workflows that can be invoked in both your Data and Business Layers.
We allow for Web and T-SQL invocation methods.
You can find out more detail on Warewolf’s intended use and general architecture here : http://warewolf.io/architecture-documentation.php
You can find out more on Web and T-SQL invocation by looking at the Samples directory where you installed Warewolf. E.G. C:\Program Files (x86)\Warewolf

You need to use it at your service layer. All Workflows are hosted as web services that can return XML or JSON data.

For example you have a workflow called MyWorkflow you want to invoke from C#. You need to use a WebRequest to invoke the Warewolf service via a URL like http://localhost:3142/services/MyWorkflow.xml

You can then take the response data and parse the XML into an object. 
Or you could change the extension from .xml to .json like http://localhost:3142/services/MyWorkflow.json
This will cause the service to return JSON data you can convert to POCO object with a JSON libary like the one here http://james.newtonking.com/json
you can then use this POCO in your C# application. 

All workflows are re-usable via the Explorer in the Studio.
You just need to drag it from the explorer onto your new workflow to re-use it.

Be sure to map your inputs and outputs when re-using a workflow.

Currently (Beta) Workflows are version-ed automaticaly and stored for later use. The retrieval process is manual but we are working on an interface to make it simple.

Currently this is not possible. Once a workflow has been called, it will run its course given the inputs provided.
Once the User interaction (Webpages) piece is done, you will be able to interact with the workflow if its built into the process.

No we do not. We currently only support flowcharts.

At this point in time we do not support human interaction.
Hence why you need to enter all data up front.

Absolutely. This is the logical next step for the system and plans are underway for a pre v1 release of this functionality. If you have any requirements, please leave them as comments here or as suggestions.

Great question that deserves a simple answer.

We do not know.

We want to keep Warewolf Free. We see it as a tool in the back pocket of every dev team. Because we cannot guarantee what the long term pricing is at this stage, and we understand your concern, we will guarantee that it will never be above $500 per year for installations prior to licencing.

We will offer support. Either through this forum, the community or if necessary contractually. If you would like to discuss further please send us your details and we will get in touch.