1. How my body reacts to the initial shock of freezing-cold water, so I know what to expect if it happens for real.
2. How my body reacts to the cold, so I have a better understanding of how fast I'd loose my core heat.
3. That I would have been OK if I had been in the ice water longer, because, although I was very cold afterward, I was not shivering.
4. That my ice spikes work. It would have been very difficult to crawl out of the water without them. They could be a lifesaver.
5. That fleece, although better than most fabrics, doesn't do a great job of insolating you when wet; my legs were freezing cold under my fleece pants.
6. That it would be much tougher to get out of the hole if the surrounding ice was weak; I put a good amount of pressure on the ice while climbing out.
7. That I can survive. Being able to think rationally in a situation like this is what saves you, and after this test I gained confidence knowing that I could rescue myself if this happens for real.