There have been many complaints about Heroes IV not being as good as expected but I think it's cool. I've completed 2 of the 6 campaigns and all I can say is that I like almost all of the changes and so it is overall a better game tactically/strategically than HOMM 3. It is brilliant that you can get heroes into combat properly cos when they get high level they are tougher than black dragons. The skill system is MUCH better and Sir Michael was wrong though, there are now 5 skill levels in each skill as opposed to 3 (basic, advanced, expert, master, grandmaster). There are also loads more skills so heroes will be truly different. For example druids can get things like Summoning which at Grandmaster level means that elementals appear in their army every day for free. Then you can get Stealth which means your hero is invisible on the adventure map unless you have scouting so you can go and steal all your oponents mines without being seen
It's also cool how some creatures are now purely spellcasters like Mages and Water Elementals and they actually have spell points and spell books like heroes so you can choose spells etc.
I think it's worth getting, it'll especially be great when the multiplayer patch comes out.