Someone said they did it:
We never got an answer so I thought I'd ask for those of us wanting to go back to Gingerbread.
Hello , i brought my brand new Galaxy s2 gt-i9100 one mounth ago . The phone keeps crashing on black screen and i have to remove the battery so i can turn it on again . Another problem also occured 3 times this mounth ... for example last night i went to sleep and the phone had around 40% of its battery left .