First off, great game, if this is what you call "very Beta" I can't wait for the next phases. I've seen games released that have more problems than this beta.

As far as the engine goes, I've had no issues with stability, so if that's all the information you're looking for at this phase, it works, and how.

The only real graphics related issue I've had is when two Rooks are fighting.  The two models run into one another and you can't tell where one stops and the other starts.  It can complicate things when you're trying to use a power on something that's standing inside you.

The AI seems to work pretty well, however I've had several issues with the comp players on my team just standing next to the healing crystal for several minutes at a time, I'm not sure if it happens when they re-spawn or go to heal.  Eventually they go back to their usual, but until then nothing gets them to move.  Once I saw both the ally comps standing idly next to the crystal while the enemy creeps attacked our stronghold, and they were within attack range for the demigods (both torchbearers).

On the subject of AI, I had one suggestion. I don't mind the fact that you can't control your creeps, but would it be possible for them to have some reaction to the presence of allied demigods?  It would be neat if the creeps had a tendency to follow/group around friendly demigods.  It just seems kinda odd that they would basically ignore the warriors that are trying to break their age-old stalemate.