I believe I am on 2771. I have not noticed any improvement in the image. I believe Capture Your Action mentioned the last update improved clip selection from the menu's.
I tried it for a few weeks. I went back to stock. I saw very little difference in the picture.
I like keeping up to date and using the latest firmware available.
If you are really particular about your glass, this stuff is fantastic for removing impossible to remove crap:
(Never goes near the car :) , but I use it on the Nissan a few times a year.)
As a general rule, the closer the lens is to the glass, the less of a problem you will have with interior reflections.
A CPL will always reduce the amount of light available so while some cameras will compensate at night, I'd still recommend it be removed.