Having completed the game 100% on Iron mode & playing that other character for awhile, I was really impressed with the game, how it played and so on. I'll make a little list of things I like / don't like about the game:

Things I liked:

The game-play was very nice for a 2d zombie game, and the weapons were fun to use in slicing, shooting & exploding the Zombies all about. It has a very nice feel I haven't felt from games in awhile, and makes you WANT to complete it.
The story was weird but a nice weird to keep people interested, and the cameo's were funny as well.
I liked "The impossible bricks" when collecting the stone fragments, because even though it was very hard, when you finally did the satisfaction was immense.
The music was HARDCORE and made of win.
Most of the guns were made of win.

Things I didn't like:

The Alt-fire of the Saw-blade cannon is way to overpowered. Even though it has limited range, you can go through the entire game (if you're re-playing) just using this one gun, since it's ammo very rarely runs out, you nearly always get more from zombies & most zombies run towards you anyway.
The lack of total darkness was a bit of a let down. In places like the subway, The prison (both of them) and Crystal lake the darkness wasn't dark enough, since you could still see all the Zombies on-screen anyway even if they was out of the torch vision. Being not be able to see outside the range of your torch in these very dark places would be challenging & fun to do (for me anyway).
The final boss music change from the 2nd form to last form was sad

Let me say about things which you don't like:
1. Unless you're not re-playing. In final stages is not real overpowered (IMO Icicle Gun is real powerful with max power-ups and with alt-fire glitch, unlike with other weapong with max "stuff"). I don't know why you're telling about one gun. On re-playing almost all weapons are overpowered (unless they're not in level 3 or you haven't powered up them).
2. On Crystal Lake my eyes wasn't able to see enemies out of the torch vision. In Hell version I could see them, but when they're staying below windows. Haven't your monitor's display to bright?
3. Sad? I don't know what you're mean. IMO it perfectly fits this music change.

I've got one thing what I don't like in GG2: is Iron Maiden in Story Mode not too easy? Perhaps I have fool minds. Well I've beat Iji in 100% too - "Immortal" difficulty completed and all Extras unlocked. I've expected more challenge in this GG2, but I've enjoyed this game much better than Iji, even I consider this game as the best freeware game nonetheless. Because it's fast-paced unlike Iji, replayability is very very high and... for long time I searched a decent game with zombies

Mike wrote:2. On Crystal Lake my eyes wasn't able to see enemies out of the torch vision. In Hell version I could see them, but when they're staying below windows. Haven't your monitor's display to bright?

I just set the Brightness to 0 & contrast to 60, I could still see all the zombies on the screen. Not as well when they are in the torch light, but enough to identify which ones are which & where.

3rhaps I have fool minds. Well I've beat Iji in 100% too - "Immortal" difficulty completed and all Extras unlocked. I've expected more challenge in this GG2, but I've enjoyed this game much better than Iji, even I consider this game as the best freeware game nonetheless. Because it's fast-paced unlike Iji, replayability is very very high and... for long time I searched a decent game with zombies

Yea I did find the Iron maiden mode a bit easy, even though you get less HP & power orbs, the zombies aren't ferocious enough and die just like normal mode. It is a great game though, one of the best indie games I have played in ages.