I bought HOMM 4 (that's Heroes of Might and Magic 4) on a whim recently and gave it a whirl. I really liked 2 and 3, so I figured I couldn't go wrong.
I was wrong about not going wrong.
Oh, sure, the graphics are very nice. All the little animations are very sharp. They also stress out my poor 16mb video card. A couple of nice minor features have been added, such as a "recruit all" button, caravans, and progressive creature mustering (instead of everything once a week). Now for the really bad news:
Sieges are a complete disaster. I'd like to slap the programmer(s) in charge of designing this portion of the game. You can now attack through walls! Some other things are screwed up to. In order for flying creatures to fly over the wall, they have to spend a turn adjacent to the wall (where, of course, they can now be attacked). So far as I can tell, a human player's creatures can't fly over the wall *at all* until the gate has been destroyed, which makes no damn sense whatsoever.
Allowing heroes in combat is interesting. I kinda like it, but in the early going they are often a liability, while in the later going they are perhaps too tough.
The siege issues didn't bug me too badly until it totally screwed me in a campaign game. After that, I removed it from my hard drive.
Thumbs Down!