After testing v20 since it was released, I can say that I'm very satisfied about it but, though at first I had thought that my cpu was able to bear the vdd levels of the option "undervolting", now I have experienced several random reboots, wlods and fcs, so I used the customization pack to remove undervolting and everything works fine.
Besides, I have been testing the rom with ferakernel, doomkernel and thkernel, either with the cpu clocked to 998-128 and to 1114-245 Mhz and I can say that my phone (maybe for another phone it could be different) likes thkernel more than the other ones. I mean it is much less laggy, especially when not overclocked, and the power consumption is very low. Even playing heavy games is smoother (I suppose because of higher vvd values).
I'd like to know why, but it is not easy to find the differences between the three kernels and I'm not able to get the sources and read the code.
Just a tip, in order to know whether your phone likes undervolting or not: put the photo widget on to the screen and put the phone in standby and reactivate it, go on for 3 or 4 times... If you have many photos in the sdcard, the widget will become very laggy. If you modify the vdd levels, you'll notice a well remarkable difference: at least, I did