1) Races often do improper research - many going far into the research tree without researching weapons (this often combines with the "surrender" option where an entire empire surrenders to another before almost any of their planets are taken or they make an attempt to defend)
2) Races do not expand properly - many staying gimped throughout the game - either by not expanding, or by expanding and then doing nothing with the planets or building enough ships to defend/attack
3) Races do not build on planets properly (if at all); some leave planets completely barren throughout the entire game, others build wrong buildings on wrong bonuses
4) Races often don't make ships with weapons or with defenses, complete lack of balance for most races (I just played one game where the Thalans had researched large ships and then outfitted them with 4 pts of lasers ..... )
5) Tech costs inexplicably double - wreaking havoc for AI and player
There's a few to get started... give me a bit and I'll list more.
That list alone, taken all together, makes games predictable and deeply (deeply!) flawed. The Terrans, the Krynn, sometimes the Altarians and Drath will usually put up a fight or dominate; the Thalans will expand like crazy and then just get obliterated b/c they are too stupid to do anything; the Arcaeans (sp?), the Drengin and often the Korath will not expand sufficiently, not just in ONE game but in EVERY game - the races act idiotically or overpowered like clockwork.
Compare this to Dark Avatar where the majority of races faired well depending mostly on luck, planet quality etc - as it should be. They all played relatively smart and managed their planets/resources at higher levels without cheating, but by making the most of what they were given and adjusting it. This seems utterly missing from Twilight. It has the appearance of depth in my opinion, without an AI to take advantage of it.
It has been over a year and a half and many of these huge errors are still in the game! The research bug alone that doubles weapons research is crippling and game-breaking.
These are far more than "tweaks", Syanis. And none of these issues depends on graphic cards etc. I am not considering hardware issues in this post - just programming.