For me hearing Russians and Germans speak their native languages makes the game better. If i dont understand what they say i usually ask someone who knows if it bothers me. But as im swedish, i can understand german without too many problems, and as i usually play the german side, i dont feel i should understand russian.
I never understood why people want to have "dubbed" voices. To me it lends a feeling of second rate american war films (which can be good in their own way, but those fake accents usually kill them for me).
Recently someone mentioned that not understanding what the people on your side say kills the immersion for him. That shed a little bit of light on the issue for me, but being fairly arrogant, i still think if it bothers you then learn what the words mean!
That said, as i dont have to use the mod i say go for it. It cant hurt to make the game appeal to more people!!