OK just some random thoughts then. The obvious point is that this is very much HOMM. On the strategic map it plays pretty much exactly the same; move troops to your wielders (hero units), then move them around the map, limited by movement points each turn, to pick up sacks of random goods and claim buildings that give a steady income of this and that. There are even lookout towers, XP towers, and sites that confer temporary movement buffs. So far, so HOMM.
The main difference is the magic system. Rather than generating mana or anything like that, your spells depend on various colours of essence which is generated at the start of each troop's turn and only in battle. This is crucial, because it encourages splitting your troops up so that you get more essence in a battle. The obvious negative, though, is that smaller troop sizes means they're more likely to be killed.
I'm not sure I prefer this change yet. It does take some stress out of the strategic layer - it's one less resource to worry about after all - and it makes your troops more important to you. But it also means that shorter battles are won before you even get time to generate the essence needed to cast the cooler spells. I definitely need more time to evaluate it before I come to any conclusions though.
One of the best things about the game is the presentation. You wouldn't think it was in early access. With the exception of the occasional typo the game is very highly polished. No bugs, graphical artifacts or anything. Music is generic but pleasant and sounds are fine. This is a game that looks a lot better in motion than in screenshots, I really cannot emphasise that enough. The UI is snappy as hell too; everything is incredibly responsive, whether you're moving troops in a battle or selecting buildings to upgrade in your city.
Anyway I've only done the first campaign mission then about 30 turns of a skirmish map so I have to withhold judgement for the time being - but early impressions are extremely positive!