I would like to take the opportunity to add my voice to the chorus of grateful users of Total Realism. Really great job, guys. Kudos!
Prompted by earlier posts concerning the late availability of cottage building, I would like to add that this is one of the main selling points of this mod, in my opinion. It forces the player to be much more careful and deliberate in the early phase of the game. When you compare Civ4 to Civ3, one of the most striking differences is the economic draught that hits you if you expand too fast in the beginning. Total Realism enhances this difference. I would hate to see this changed.
That comment may make it obvious that I don't use the mercenary options. From the comments I have read, it is hopelessly unbalanced, giving a source of income way out of proportion. If you need hints on how to balance this income, maybe you could look at the amount of money a city can produce when converting production to cash. Producing troops and hiring them out should not make a lot more income than this, I think.
I would also agree with some previous posts that the Assassin unit is overpowered. The tech stealing is not so bad - it allows you to catch up if you're behind in the tech race, but if you're in that unfortunate position, I think the extra help is appropriate

But the ability to cause civil disorder is too much. Not only can you wreck the economy of opponents, but using the assassins to induce civil disorder in border cities of an opponent allows you to move your units right up to the city gates before the war declaration. The civil disorder will also remove the defense bonus of the city, allowing your siege units to concentrate on causing collateral damage to the defenders. Used this way, the assassins enable the player to cause a devastating first strike, taking out many or all of the border cities, along with their defending units, with little or no casualties. Leaving an opponent that may be effectively broken after the initial turn of war.
I don't think this use of the assassin unit as a key component of a blitz strategy was intended. And obviously, the AI is not equipped to use it in this way. Thank God! Which brings me to the matter of defending against assassins. Which seems nearly impossible. One defending assassin does not really decrease the success chance that much, and adding more doesn't produce a linear increase of the defense. And besides, your capitol will be busy enough producing one assassin for each of your cities, in addition to those you use offensively. I like the suggestion to enable attacking assassins without declaration of war. I think that would neatly take care of the defense issue. As for the overpowered offensive capabilities, I am not sure what to do. Perhaps reduce the ability to cause civil disorder, or add a cost to activate that ability...
Last comment about assassins: I suspect there may be a bug in the activation code. In my current game I experience a lot more failures than expected against a certain opponent (Chinese, NOT police state). The results seem consistent with what I'd expect IF he had police state... But I've checked that several times, he doesn't... By the way, it would also be nice if the tech stealing code reported if there were no techs to steal.
Further feedback:
I like the stack aid. This is a real nice enhancement of tactical play. There are some doubts in my mind though... Like, if a unit in a stack attacks a unit that is not in a neighbouring plot (ie. using roads or having 2+ movement points), will it retain the stack bonus? I seem to lose a lot of battles that I should have 90% or better chances of winning, according to the odds displayed when I right-click on the target... this might be explained by the unit losing the stack bonus immediately after leaving the stack. I think it would be better if the stack bonus was only updated during the turn calculation. That would also prevent certain exploits, like moving a unit (could be a leader) from stack to stack, allowing the stacked units to take advantage of the bonus in their attacks, before the leader/unit moves on to the next stack. Is that really an exploit? Well, it feels like it
All in all I love this mod pack. I wouldn't want to live without it. Keep up the good work
