The fourth game in the series is a classic case of "every family has its black sheep." It's good, no doubt about it, but there are far more downsides! :( Firstly: it is painfully similar to Warlords. Thank God not in terms of graphics. Secondly: the AI is godawfully stupid! Why the hell does it either stay stuck in the Castle or ignore mines and resources right under its nose? Battles with the computer boil down to destroying lone units, minor heroes, and as the pinnacle of this absurdity, storming cities where the computer spent the entire game hoarding units for no apparent reason.
Thirdly: the music! Why does the same track play when a hero is wandering the map, regardless of what terrain they are crossing? This is a gross violation of tradition! Fourthly: where did the upgrades go, and what's with this moronic system of "excluding" units from the Castle? It's like attaching a mixer to a vacuum cleaner. No use at all, but original!

In short, it needs major overhauls that no one is going to do anymore. What was pleasing is the powerful and intuitive scripting language.