Thank you all. The first thing I did with your instructions is the nandroid. I don't actually need it 'cause I stay with october release and it is perfect, no problem at all with anything. I asked just to know for those who messed up with new versions and would like to get back due to many problems they have. I'll report the simple use of sp flash tool and version on forums where I attend.
Thank you! I actually mean: how does it perform?
Since the stock rom seems to be the best for performance and stability, I will upgrade it when there are real improvements, not just 'cause I like to do so...... :-)