The Little Brown Keg has lots of nooks and crannies that can be hard to clean. If you choose to use it on a wild fermentation, I highly recommend that you only use it for that purpose from now on.
Also, as a secondary, remember that even thick, dark plastic is still somewhat permeable to oxygen. Depending on how long you intend to secondary your beer, you may wind up with some oxidation and, possibly, aerobic bugs in your finished product. Plan accordingly.