While I was one of the early and consistant proponents of seperating the scoring, it's funny that two days ago I decided I should post opposing it (but didn't get around to it).
Now that it will become reality, I know for my own part, that my trips to EW, while currently limited to once or twice a month will become zero times per month while my trips to MW will be limited to the minimum number of missions required to achive score in each catagory.
While initially, my purposes for visiting these arenas was to sneak unopposed base captures (which, BTW, became ridiculously high) to keep up with the "regulars" in these arenas to maintain my vehicle/bomber rankings, I most often found myself doing much more... fighter missions (yes, a few there do fly fighters and actually like to fight), attack missions and vehicle base defense missions.
I now think that ultimately, this move will further reduce and limit the number of players visiting these arenas. I fear their demise is quickly approaching and MW, at least, was fun if the numbers were decent (30+).
Besides that... two less maps to choose from playing on.