Loading a Swift dictionary from a plist file

One of the things that doesn't seem to be there out of the box is serialisation support for dictionaries. This function uses NSPropertyListSerialization to achieve that returning  Dictionary<String,AnyObject!>? 

import Foundation

func readDictionaryFromFile(filePath:String) -> Dictionary<String,AnyObject!>? {
     var anError : NSError?

     let data : NSData! = NSData.dataWithContentsOfFile(filePath, options: NSDataReadingOptions.DataReadingUncached, error: &anError)

     if let theError = anError{
          return nil
     }

     let dict : AnyObject! = NSPropertyListSerialization.propertyListWithData(data, options: 0,format: nil, error: &anError)

     if dict{
          if let ocDictionary = dict as? NSDictionary {
               var swiftDict : Dictionary<String,AnyObject!> = Dictionary<String,AnyObject!>()
               for key : AnyObject in ocDictionary.allKeys{
                    let stringKey : String = key as String 

                    if let keyValue : AnyObject = ocDictionary.valueForKey(stringKey){
                         swiftDict[stringKey] = keyValue
                    }
               }
               return swiftDict
          } else {
               return nil
          }
     } else if let theError = anError {
          println("Sorry, couldn't read the file \(filePath.lastPathComponent):\n\t"+theError.localizedDescription)
     }
     return nil
}

let dictionaryFilePath = "/Users/you/your.plist"

if let loadedDictionary = readDictionaryFromFile(dictionaryFilePath){
     println(loadedDictionary.description)
}

It's worth noting I'm not doing a deep conversion (that is the contained NSObjects are not being converted to native swift objects) because it is not clear to me that that is always desirable.