I have stock V20Q with a Flix123 performance pack, no custom kernel no custom rom, and am very stisfied (smooth, efficient, no bugs).
I tested all the roms available in XDA dev (CM7, CM9 and custom stock) but no one is stable and full functions like the 20Q one. If you start with these roms and have probles is better that you give up.
You may update your rom and baseband using LG Mobile in your country.
In order to have better efficiency, I also freezed in Titanium backup some unused system applications (kit auto, google talk, f-secure antivirus, Email, backup, LG PC suite); no antivirus installed, installed only the used applications and not the nice to have ones, no application killer (android take care of freeing ram).
I second this !!!!