Can't get list of values for some picklists

Question

I think any field that has data tye Picklist (read-only) in Opportunity Field setup, does not allow to get PicklistValues.
How else are we supposed to get a list of possible SalesStages through the API?!
Here is a generic code (c#) I am running using mapping/picklist wsdl to get all Picklist fields on Opportunity and get list of their values. Some work just fine and other reutrn exception that the field is not a pick list (and those are ones marked as Picklist(read-only) ). Any help is appreciated. Sorry if formatting gets messed up.
Mapping mapping = new Mapping();
MappingWS_GetMapping_Input mapIn = new MappingWS_GetMapping_Input();
mapIn.ObjectName = "Opportunity";
mapping.Url = this.Session.GetURL();
MappingWS_GetMapping_Output mapOut = mapping.GetMapping(mapIn);
foreach (Field aField in mapOut.ListOfField)
Console.WriteLine("Name: " + aField.ElementName + "\tType: " + aField.DataType);
if (aField.DataType.Equals("Picklist"))
try
Picklist picklist = new Picklist();
PicklistWS_GetPicklistValues_Input plIn = new PicklistWS_GetPicklistValues_Input();
plIn.FieldName = aField.ElementName;
plIn.RecordType = "Opportunity";
//plIn.LanguageCode = "ENU";
picklist.Url = this.Session.GetURL();
PicklistWS_GetPicklistValues_Output plOut = picklist.GetPicklistValues(plIn);
foreach (ParentPicklistValue aParentValue in plOut.ListOfParentPicklistValue)
Console.WriteLine("--Name: " + aParentValue.ParentFieldName + "(" + aParentValue.ParentCode + ")\t Value: " + aParentValue.ParentDisplayValue);
foreach (PicklistValue aValue in aParentValue.ListOfPicklistValue)
Console.WriteLine("----Value: " + aValue.DisplayValue + " (" + aValue.Code + ")");
catch (Exception excc)
Console.WriteLine(excc.ToString());
}

Answer 1

OK, we just ran into this issue as well. Sales Stage is, in fact, a "Picklist" (as revealed by your own metadata API), its values can change and as such its items should be made available via the API. Hard-coding is a hack, pure and simple. I suspect this is not the only picklist that the services fails on; Is there a document anywhere that indicates which picklists do not have items available via the service API?
Thanks.