I just had my first loss to hiberation, I had 5 2003 russians hibernating in one of the shadier raised beds in my garden. All 5 woke up early, by the time I noticed one had perished. The other 4 are well.
I'v had over 80 hibernations and this is my first loss, I don't want to discourage anyone from letting them hibernate.
If you live in the San Fransisco bay area or a similar climate, and have any tortoises hibernating outside its a good idea to start checking for them. The other 35 or so hibernating in other parts of my yard are still sleeping.