While trying out the new snapshot I noticed that pistons seemingly randomly got stuck in extended position. With this I don't mean the usual "bug" exploited by several BUD-switches. In this case one could destroy all blocks around (I destroyed all blocks in a radius of 3 around them) place and remove blocks adjacent, power them and then remove the power source, ... there was seemingly no way to retract it, once stuck. I also could not make out any pattern which situation may cause this bug. Seemed to be completely random.

Edit 9th January 2013 9:40 AM:
Managed to recreate the issue! Posted screeshots how to recreate it!