I played through a long game this weekend (as pariden) and experienced a number of problems that all appear related to the tactical battle screen.

* Black screens and game crashes all occured coming out of the tactical battle screen.  Memory leak problem?

* As game slowed down, units in tactical battle screen would start having their status bars fuzz into a multi-color rectangles.

* Auto-snap feature is buggy:  when I first click to initiate combat on the main map, the map snaps to next unit just as the tactical battle screen opens.  When leveling-up heroes after a battle, the map keeps snapping to the next unit before coming back to the hero that is leveling up.  Very annoying.

* During a battle, defend (shield icon) is broken.  After pressing the shield icon, a selection pointer strangely appears but doesn't do anything and the game waits for ~10 sec before moving on. 

On another note, I still think the research progression is way too slow on normal mode; after many many hours I hadn't even researched half of the tech tree.  Strange to be at end-game with leather armor.  I really like the new shop/trade interface, though.  I hope these tactical battle screen problems can be resolved.