found a good link to a page explaining walking through an IEnumerable yourself Unity3D coroutines in detail

that I thought might help, but haven't had much luck... still loops through with WWW.isDone = false and no error in WWW.error.

but, wasn't able to get it to effectively block until download was complete with the following code...

    public WWW RequestAndWaitForLoad (string url)
    {     
    isLoadingBundle = true;
    Debug.Log(String.Format("##WWW requesting {0}", url));     


    int test = 0;
    IEnumerator e = FinishDownload(url);
    while(e.MoveNext()) 
    { 
       Debug.Log(String.Format("##count:{0}", test++));
    }   

    Debug.Log(String.Format("##RequestAndWaitForLoad after startcorouting "));     
    Debug.Log(String.Format("##isLoadingBundle is {0}", isLoadingBundle));     
    Debug.Log(String.Format("##wwwResults is {0} null", wwwResults == null ? "" : "NOT"));
    return wwwResults;     
}


protected IEnumerator FinishDownload(string url)
{
    WWW theWWW = new WWW(url);     
    if(theWWW.error != null)
    {
       Debug.Log(String.Format("##FinishDownload breaking with error : {0}", theWWW.error));
       yield break;            
    }
    yield return theWWW;     

    Debug.Log(String.Format("##FinishDownload Ater first yield isDone is  : {0}", theWWW.isDone));
    if(theWWW.error != null)     
    {
       Debug.Log(String.Format("##FinishDownload Ater first yield isDone is  : {0}", theWWW.isDone));              
    }

    wwwResults = theWWW;
    yield break;     
}

I'm afraid that would be a lot of code. The key hangup, however, is that we have code throughout similar to

levelConfigXML =  ResourceController.INSTANCE.Load("level1config.xml");
// parse levelConfigXML and assume it's already been loaded

// Below is pseudo code

class AssetBundleResourceLoader : IResourceController
{
   WWW bundleLoader; 
   String CurrBundleName;
   Object Load(string path)
   {
      String bundleName  = GetBundleFromPath(path);
      if(bundleName != CurrBundleName)
      {
         bundleLoader = RequestController.RequestAndWaitForLoad(CurrBundleName);
      }
      Object result = null;
      if(bundleLoader != null && bundleLoader.error == null && bundleLoader.isDone)
      {
          if(bundleLoader.assetBundle != null)
          {
              result = bundleLoader.assetBundle.Load(path);
          }
       }
       if(result == null)
       {
          // fallback to "parent" loader
          result = base.Load(path);
       }
    return result;
  }

  class WWWRequestController
  {  
     WWW RequestAndWaitForLoad(string url)
     {
        // have made many attempts here to essentially start a d/l of bundle and "wait" for it to complete. How have others solved this?
     }
   }

{

}