Just finished the whole campaign on Normal (not the newest version though). Here are my thoughts:
Chapter 1 - Edited map of Stratholme is really nice idea. I know that the first map should be easy, but I think this one is too easy.
Chapter 2 - You should add a timer or something like that to the base building part. The undead army is coming, but I can spend even a hour on building a whole army of towers. Yay!
Chapter 3 - Cool dungeon level. Nothing much to say here.
Chapter 4 - The High Elf race is nice, shame that it's playable only once during the campaign. The only issue about this map is that the about half of the map is empty

Chapter 5 - I really liked the idea of hiring normal human units in tavern. Arthas gains a new spell here, but it disappears in the later chapters

Chapter 6 - This one is too easy, especially when purple is defeated. Also, I failed the optional quest because I didn't discover it earlier (?!).
Chapter 7 - The troll race is cool, but (again) it's too easy to kill them.
Chapter 8 - The best map of this campaign. It's challenging, it has excellent terrain (especially in the city part) and there's a plot twist at the end. More maps like this one please!

Chapter 9 - Well... It's a bit boring. If I were you, I would decrease HP of the buildings and change the quest requirement to 'Destroy 5 Fortresses' or something like this. The final boss is way too strong. Just remove Mask of Death, decrease HP and add some small creeps around him and it should be OK.
To sum things up: it's fun campaign, but it has some minor faults. I don't rate it for now, maybe I'll do it later when you improve it.
And don't get me wrong if I'm a bit rude. I just want to help you make this campaign perfect