I always enjoyed thevery board game. I also enjoy this mobile version. The graphics and gui are nice and simple without feeling too sterile like some of the offshoots I've seen on Googleplay.
However I think the areas that need improvement which would most help get more people playing are in the areas of difficulty and most importantly online play.
The aI still seems a little predictable in where it's going to attack. It feels more like an exercise in graph theory. I don't know enough about ai to suggest where to go with that but I think the online multi-player aspect might be a better solution to the same problem of difficulty. Working on the multiplayer mechanics might facilitate the solution of difficulty quicker through the unpredictability and variety of strategies you come across when playing other people. It seems as though going the route of putting out ai revisions would be more trial and error.
As far as features for the multi-player probably just developing a better/quicker random player match up would do the trick to start.
Hope that helps