~ Sound- The sound is excellent. If not for the memory problems (see below) occasionally distorting it, this would be one of the better video game scores I've encountered. The opera in the towns ranges from very good to flawless (in particular, I thought the Death town score was amazing). Sound effects are generic but adequate. The voice acting is sparse but well done. Overall, the sound is one of the high points of the game.
~ Interface- The interface is utilitarian and efficient. Keyboard shortcuts exist to just about everything, but if you don't want to learn them, it's very easy to play the game mouse-only. The only time the interface gets irritating is when they have slider bars, a problem that existed in previous HoMMs too. It's a pain in the ass to sell a certain portion or split troops a certain way without clicking out the exact numbers. Clicking at the center point of the slider bar tends to cause it to jump over the cursor, rather than (gasp!) where you actually clicked. Double-clicking can be a little touchy as well, particularly when trying to move an army on the overland map. For the most part, it's unchanged from previous editions of the game, and does what it has to do with minimal fuss.
~ Replay value- They've continued the same system of campaign design that they started in HoMM3 and perfected in Armageddon's Blade, so the campaigns are extremely intensive and long-lasting. The included single scenarios are well designed and varied. The big replayability factor is multiplayer, which is lacking from the release version of the game. This, coupled with the earlier mentioned graphical incompleteness, points to the game being released unfinished, which always annoys the shit out of me since it communicates a large amount of contempt for the consumer from the releasing company. 3do has promised multiplayer support is on its way in a patch. Considering HoMM3 was the best Hot Seat mutliplayer game since Scorched Earth, I certainly hope so.
~ Gameplay- I thought HoMM3 stood out as one of the best designed games in recent years. If HoMM4 had kept the engine and just added some new features it would've been a fine game. As is the nature of designers, however, they felt the need to tinker extensively. The gameplay remains very solid and in places even improved, but sadly some of the game loses quite a bit of luster.
Plusses: The combat system of the game is superbly balanced now. They've managed to differentiate the various town types significantly in the tactics they use, and heroes are more of a deciding edge rather than the overpowering factor that they were previously. Quite often I felt like I'd won because of superior tactics rather than because I had better/more monsters, and that's a good feeling. The storyline (which I believe ties into the now-godawful Might and Magic games) is interesting but makes no fundemental difference in the game from previous editions. The writing in "cutscenes" (really just text boxes) is surprisingly good. For some campaigns they've adopted the peripheral-character-as-narrarator technique (much like the Myth games), which I think works well. I actually got interested in the characters, which is a lot more than I can say for the previous HoMM games. The level design is also very good, with maps that are challenging and full of interaction but never overpoweringly complex like some of the Armageddon's Blade maps. The skill and magic systems are pretty much intact, with a few neat new ones (Resurrection is sick, Stealth will be sick against non-cheaty-AI human opponents) and a few old favorites gone (oh Logistics, why did you have to go and have a bastard child with Pathfinding?). They managed to cut out most of the totally useless skills and beef up the ones that are only useful in certain situations.
Minuses: Pacing, Pacing, PACING. The entire game is terribly out of synch. The designers had serious temporal perception issues, that's for damn certain. While the game has a bevy of speed options, it always seems that some things are going too fast and others too slow. In combat, for example, monsters and heroes walk painfully slowly on the default speed. Put the speed up a few notches and they walk around at a more reasonable pace, but their attack animations are nigh-instantaneous and impossible to discern, and damage numbers flash by too briefly. The main issue besides this is some sort of major memory problem (some have called it a memory leak, I won't pretend I know enough about it to identify it). Over the course of playing the game, my swap files just got more and more filled up, and after it had been running for a few hours, performance slowed to a crawl. Quitting and restarting the program took care of it. It's probably going to be fixed by the first patch, but since 3do is notoriously awful about supporting their games, who knows when that'll be. The game also has assorted minor design flaws. The hex grid is gone from combat, making troop positioning largely guesstimation-based. Help windows are either nonexistent or just not very helpful. While the storyline text is excellent, most of the lesser flavor text is extremely spartan. Early on in scenarios it can take a LOOOOOOONG time to gather the resources and army to get beyond "Run out and have a fight, run back home to recuperate".
~ Overall gameplay: Very good, but pacing is a pain in the ass and you may have to restart periodically. No flaws really beyond annoyance level.
~ Enjoyment- The HoMM games have a formula that works, and that formula, coupled with excellent writing and marred only by minor flaws, made this game highly addictive and a major time-eater. It occasionally gets slow, with multiple turns of meaningless little battles or resource gathering, but that's rare.
~ Changes(++)- Fortunately, the changes in HoMM4 were positive for the most part. The biggest and most highly touted is the fact that heroes are actual units now. I thought they handled this aspect perfectly. Heroes are just the right strength, early on and as the game progresses. The hero advancement system has also changed. Instead of being static, the hero's class is determined by the two most highly-specialized skill groups they have. This gives you a lot more control over what your heroes' abilities are. The main negative change with heroes is that they are all generic (ie- one ranger is identical to any other ranger with the same skills). I thought the per-hero skills from HoMM3 were very nice.
Towns have changed quite a bit, and besides caravans I think the changes are very negative. Creature generation has been dumbed-down. Each town can have 5 creature generation spots, with all but the first level being a choice of two possibilities. This makes assembling interesting, varied armies a huge pain in the ass, especially on smaller maps. Resource costs of everything have changed dramatically, some for the better (affordable magic guilds) and some for the worse (outrageously expensive blacksmiths, creature generators). The gigantic positive change in towns is the introduction of caravans. These take almost all the hassle out of utilizing external creature dwellings and massing armies from many towns into one. This plus the fact that monsters no longer need heroes to lead them around make the external creature dwellings vastly more useful (they were generally too much of a logistics pain to bother with in HoMM2+3).
The graphics improved somewhat but not across the board. Towns are airier but missing a lot of the fine detail that made them so interesting in HoMM3. The isometric combat view means that the terrain is much more vivid, but the creatures and heroes are hit and miss.
The sound is a huge step up, a fine mesh of the best aspects of HoMM3's and HoMM2's respective sound tracks.
Finally, adding the retention of last turn's autosave is invaluable.
~ Swear word rating: 1 per hour, generally from interface bloopers
Overall: 8.4, worth buying immediately.