I'm not certain I can speak for all of tbose other players, but I think we all had mostly the same problems with the game.

Power due to leader cards: I've seen the cards change fairly often. Losing the Military Leadership is easy, as you only need to lose a few units. Losing the other's is fairly easy as a matter of conquest, since occupied cities count for the occupier.

I actually felt the Military leadership was most powerful, although most volatile. Political leadership also has it's points, both due to the advantage of having lots of taxes, and the edge in building the final building to win (although this can just make you a target). Political leadership definitely seems the weakest, although then again I've seen its holder win most often (although I suspect this is due to lack of experience with the game).

The supply of chips for cities. After the chips run out: But then temples are still available, plus if there were any more taxes available they would be too much of an advantage. Besides, it seems reasonable to me that if you want more cities, you must invade.

Piling on a leader and not quite knocking him out of the game: This is quite true, although IMHO it's not necessarily in one's interest to do so, as going that far typically lets someone else jump ahead. In fact I've seen all the games I've played have such moves get punished, as it's very difficult to both attack and defend.

In retrospect, most of the players seemed to agree that the way to play the game is to be hyper-aggressive on the military front, yet when you first learn the game it suggests that trading is what the game is about. If they're right and building a strong military is what the game is supposed to be about... then few of them want to play it. If we wanted to just throw our armies at one another, we'd play Risk. =) In my opinion, the trading is what should make the game interesting, but the game doesn't work that way.

The 3 or 4 games I've played have all been won by non military players. They of course still needed to build some military units, but they didn't win through conquest. Being very aggressive either makes you a big target, or puts you in the unenviable position of being the only one capable of stopping another player from winning. The attritive nature of combat plays a strong part in this, as armies are expensive, you can't build very many, and any potential benefits are delayed at least a turn even in a complete victory.

In my humble opinion, Mare Nostrum is a Civilization Lite, although the lack of technology is a sore point for me; but then again we've always finished in under 3 hours. I like Civilization a lot, but it's just too hard to get enough players willing to devote the entire day to playing it. :-(