I really enjoyed Disciples 2 Gold: the maps, cities, chess-like battles- I thought it was a fun game. Disciples 3 seems to have traded some of the simple-but-functional game elements that worked so well in D2 for fancier graphics in D3.
In D3, the game world looks really nice but items you can loot / interact with on the world map are not always obvious (unlike D2). Your field of view is much smaller in D3 than D2 so depending on your play style, you might dislike that (I do). Rotating the camera is nice, but scrolling the map with your mouse feels sluggish. Also, when you're planning to move a distance that requires multiple turns, your path marker no longer tells you how many turns it will take to complete. Small annoyance- but it seems like a useful feature that was removed. Also, unless I'm missing something, there are almost no keyboard shortcuts! This is kind of frustrating for me, but I'm sure some people won't mind it.
What stands out as the biggest improvement is battle. Now there is a hexagon-covered battlefield when you engage an enemy. Each of your troops can move a unique amount of hexes, and ditto for the enemy. When you mouse over the enemy, you can see their movement range, HP and Attack Power. Currently, attack power is bugged and you have to right-click on the enemy to get the real number. Kind of strange that the 1.06 version has this problem. The inclusion of battlefield obstacles like rocks and ruins is a nice touch, as are the "tactical spots" on the battle field. These spots are essentially tree stumps that will either double your melee, ranged or magic damage. These things combine to make the battle system a decent improvement over the somewhat rote combat of D2.
FYI this is based on the RU version of Disciples 3 patched to 1.06 and with english text.
edit: forgot to mention- when in battle, you can now see the order in which units take their turn. Good shit!