That's intriguing. I've been using 1.71 for a while now and definitely was able to notice a difference in NPC behavior once I installed Tony K's AI. Does your improved AI require some kind of switches to work, or something? 
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No, but since the scripts from CPP has lowest priority anything in override, module or maybe even hak (ugh) will overwrite it, in this case its nw_c2_default* set of scripts. That probably won¨t be your case though.
For instance, Tony K's melee NPCs try to knock me down, whereas I didn't observe such behavior before I installed the AI.
They spam it riddiculously often and CPP even lower the spam rate, because AI is not capable of crowd thinking so multiple monsters are knocking down one target causng weird behavior and no counterplay.
HOWEVER, this happens only when monster recognize you have too low AC, and instead of using AB they are using hitdice (total level) to check whether knockdown has sense. Its very likely that Tony changed this. Its something I was thinking about too because this behavior has no sense, however the impact on the balance especially preexisting modules seemed to me too big to do this in CPP.
Another example is that spellcasters make some good use of scrolls and wands with Tony K's, whereas vanilla spellcasters (or at least clerics - I reverted them back to the default AI for now and tested them this way) ignore these items in their inventory completely.
well, I dont think Tony really touched this. I might be wrong but he would have to make whole new "section" for this. Actually vanilla AI is capable of usng these items and scrolls, however they have a CR 0, thus AI try everthing else before using this. Thus mostly AI uses scrolls/wands when runs out of prepared spells or when its snared which cause a bug that impacts AI and make creature brainless thinking he has no spelluses.
Tony K's AI also stops spellcasters from casting offensively at all if their enemy has spell resistance that they can't get through. I was positively surprised to see such a feature and that's why I'm mentioning it here, but I don't know if your AI doesn't do this, as well; maybe it does.
No CPP is not doing this. It would be really stupid. It can look good on some creatures but if you make a caster with no melee capatibilities then what sense it has? Sure casting a spells will not likely do anything but thats in my opinion wrong design or its high lvl player in low level area. NPCs shouldnt know that they have 0% chance anyway unless its high level AI (which isnt implemented, but im adding this to my idea pool 
'>). In my opinion if monster has spells it should use them despite they are not doing anything because player has death immunity, improved evasion, high saves, or spell resistance. Only exceptons are racial limited spells and HD or hitpoinst limited spells. There are also SR ignoring spells and SR lowering spells. And what about selfbuff spells?
