First of all, I have played for several hours now without a single crash. 

Here's my latest thoughts:

• As has been mentioned by others, there are some so-called 'strong' or 'deadly' opponents that are nothing of the sort.  Ignys being the most obvious example.
• Crystal and iron are unbalanced.  If you go the crystal route with tech then even if you have 3 or more crystal resources you are struggling to make enough.  Meanwhile even with a couple of iron mines I end up swimming in the stuff fairly quickly in all my games.  I even had masses of it when I went iron route.
• Movement is frustratingly slow.  There seems to be no way (other than getting the lucky promotion) of getting movement above 2 until you research horses.  You can waste loads of turns doing nothing but making your way through a forested area until you get a hero to cloud walk 
• Speaking of cloud walk, the reason it is OP is because there is no alternative to move quickly.  Maybe there could be some sort of ability to create portals in the world, using lots of crystal?  Rather like the Vasari phase stabilisers in Sins.  Possibly a city improvement.
• Items are a bit boring at the moment.  You get a really high power object, think 'oh that was a lucky break', then ten minutes later you've got three of them.  Replayability is really hurt by the fact that you go out and get the same stuff every time.
• There should be items for increasing movement (this would help with the movement issue)