Looking at the bottom twos all the way through series four, I can't think of an example where the judges would have made a worse decision than the public did.
eg Spoony vs Georgina- I wasn't Spoony's biggest fan but it was sad that it happened to him so at least he would have had another chance
Carol vs Emma- Judges would have chosen Emma, but the way the public voted she went through anyway by default
Emma vs Peter- Judges would have chosen Emma, who was a better dancer than Peter, and who got through on the old system anyway.
Emma vs Matt- Judges would have chosen Emma, which wouldn't have been my choice, but from a dance perspective I think many people would have agreed.
So even though I think this is one of the BBCs worst ideas yet, I don't feel so bad that the judges are going to spoil things with favouritism any more than they may have in the past with dodgy marking.
I don't think I'll waste my money voting though, if I want to give to charity I'll do it directly.