I had a mini spool in my last Mustang... it didn't last too terribly long. Ended up fracturing one of the blocks, and the piece that broke off rode the ring gear around and made a neat little window in my diff cover.
A few of the larger pieces that broke off of the blocks that the axles slide into...
If you're careful with it, it might not be as bad as mine ended up. My daily driver was down at the time, and I had been driving the 'stang locked up like that on the street for about two weeks. I've seen them work just fine before, however. Maybe mine was just bad luck.