Hawk52: - The game still suffered from a serious Heroes problem. Not every unit was useful. Some units just *sucked*. This has been a problem with every Heroes game.
Virama: 2.) Waste of time combat - some units were simply annoying and could pwn your top tier units without even trying, making the whole game even more frustrating.
5.) Ridiculously overpowered hero - in particular that Undead one with the heal ability - I used to max him out asap in his regeneration and heal - every battle fought, I'd simply get hundreds of skeletons until I was unstoppable. Just too unbalanced IMO.
Actually, Heroes V with the last expansion is surprisingly balanced, and people saying that some units are useless quite simply didn't spend enough time with them. Heroes V, their current version at least, possesses one of the best tactical combat systems I have ever seen, initiative system being a large part of it. It's amazing.
I do agree about the lack of little details that made 3 amazing, however, when I wish to play a skirmish game, I will play V just for these reasons: It's more balanced (aside from the damn barbarian town), skill tree works well, all spells are useful and you can get trough the game easily even with spell-less might-focused hero.