A potential gem but needs some polish.
The best thing the new Heroes has going for it besides the feel is the advanced strategies now necessary in combat. The game is close to a full blown war sim the way you must position your troops and strategize against your enemies strengths and weaknesses. Even core troops have vital strategic traits you must pay attention to if you want to have any hope of beating a campaign. Its all about conserving troops. Even if you have superior numbers it is crucical to approach even weak neutral armies with care because trust me you will need every single one to take down the last hero in the scenario, If you lose too many, a map restart is going to be necessary. Which isn't too big of a deal except on the huge maps its quite annoying.
Here are a few troop built in abilities that offer some huge strategy elements not seen in previous Heroes games.
Sentinel shield guard: Now these core troops can do an amazing job of preserving your more delicate, but harder hitting units.
Marksman penetrating bolts: These can slice through several enemies at a time but with their great power comes great care, they also can hurt your troops.
Sister healing: Your ticket to having minimal losses early on in the game as they can actually resurrect your troops. Guard them at all times.
The later units trivialize the strategy a little bit, but overall this game is very low on the resource management and high on the field tactics, which is a good move. There is no denying the game needs work, it runs bad, has some balance issues with healing, has many beloved missing units (dragons, neutrals), and enemy AI needs tweaking. The core of the game is extremely solid though, most the rest can be patched or added in expansion. Did I mention the campaigns will give you 80 hours of play time? For the above reasons I am giving Heroes VI an 8.5, with a 9.5 potential on patches.