As I understand it the glass on the current VX-I is the same as the VX-II of 5-6 years ago...I own 2 of the older VX-IIs and have a couple of buddies that have the newer VX-Is...As far as light gathering, I can see to shoot as long as its legal (30 minutes before and after sundown)..
I have no problem with the friction adjustments, they respond properly and once set they stay set.