I personally like the talent tree system,and would've liked to see something like that put in place, in addition to the attribute system. Also, I feel that the difficulty was too low. I've played a LOT of TD games over the years, and this one was by far the easiest.
Ok, just a few quick notes. Just beat Zombogod on my 3rd try. + so people can see.
1) You can drop your dynamite on the boss' face. 2) You can't ignore your hp, because your allies aren't good enough to handle them all on their own while you focus the boss, so try to throw a clip down there every 20-30 seconds or so. 3) There are no refugees on the final level, so reset your talent points, and leave the refugee tree empty, max out everything else. 4) tibiaowns was completely right, the rocket guy attacks much faster if you leave his ammo capacity at 1, but max out this reload speed and firing speed. All player/ally abilities should be maxxed out EXCEPT Rocket Dude's ammo capacity. 5) Ignore columns, and just shoot him in the face endlessly. 6) Air strike is best saved for when the screen is full of enemies.
I didn't like this modification. I much preferred the army system over the single character system. This game really isn't designed to be played on a laptop. I don't have a numpad, so it's not very easy.
This game is a LOT like Amorphous+. But what this game really needs is a beastiary equivalent. Which one is the giga cell, and P.C., and N.C.? etc. etc.
I think that whenever you level up, the number of mobs and xp should go up. Levelled up quickly enough, didn't need to get even close to clearing the whole skill tree though. :-/