I'm not going to be repeating the version overview, you can get it from the App page or when updating. I did notice a tad more pop-ups of other SNK Playmore game advertisements at the start but didn't encounter more. I've also checked out the 2 new areas, New York and Brazil, and notably there are no POW to rescue.
I won't be spending much time in this game anymore due to Hearthstone, thus I won't be able to contribute much. I will try to complete the new Special Missions and areas whenever I have the time. Metal Slug Defense is a nice game made with good quality but I think the market is filled with many such games (high quality free to play games) that there is no time to keep playing them all... well, at least for me.