Gamespot has an online preview of Heroes of Might and Magic IV.
"One of the most notable things about Heroes IV right off the bat is how different its overworld maps and interface look. Though Heroes IV offers most of the same options and landmarks as the previous games, everything looks radically different. The build we've received runs at resolutions up to and including 1280x1024, and everything on the maps, including treasure caches, event items (like the old Heroes favorite, the learning stone, which grants 1,000 free experience points), and artifacts look completely different and far more detailed and colorful than they did in previous games.
The other tremendous change that Heroes IV makes to the series is its new combat system, which seems more tactical than in previous games."
News source: GameSpot