I have been playing for about 12 hours now and it is a pile of fun. I can see why there was no IMP as it is now a 1 time fee to hire a merc but you pay it all up front, so it is hard to start with more than 3 low end mercs. Your biggest limiter is always $$$, get another merc? a better gun? better armor? but only so much $$$ to go around. Your skills like Mechanic, Medic, and Explosives are now even more important as the merc won't even try to do something if he has no skill at it. The leveling is good and the smarter your merc is the faster he levels, if he can get some kills in.
The overland map is different as there are no more sectors but points of interest to check out and hold and once you take an area you can observe enemy movement around it and react accordingly.
I am not sure about the militia the few times they get in a fight they get wiped out, of course that could be cause I gave em crappy guns and no armor too so I will see but I'm thinking sell the guns and hire another merc or 2 and kill em all your self.
Over all I am finding it as fun as the first one better in some ways different in others, but worth the $35 I paid and these days that's usually as good as it gets.