Note that I am using a modded game based on original + CoS + Xtra. So I cant be 100% sure that all bugs posted here by me are present in the original game. I am only posting bugs here which I believe to be present in the original game though.

Just found the following:
'Produce Growth/Mana/Research' improvements are bugged in the following manner: Once placed in the pipeline the effect becomes permanently attached to the town. (It never needs to be actually produced and removing it from the pipeline does not change the attachement.) There may be related UI display/update bugs too. Like in city details window it does not show the effect of the attached 'Produce Growth' but it still has the effect when pressing 'next turn'.
'Produce Wealth' did work correctly though - although there may have been some UI update/display bug/s with it.

Wrong tech being researched bug:
Was researching 'Drills' with 1 turn left. Clicked on 'Researching' and selected all the tabs. I think without changing the researched tech, dont remember the order. Then I clicked on Cancel. Then I checked (including mouse over) if the researched technology is still the correct one (I knew that there is some kind of bugginess but wasnt sure exactly how/when/what) and the GUI (including overlay help) still said 'Drills' with 1 turn left. Then I clicked 'End Turn'. After the turn was done the game had not completed researching Drills. Instead it had started researching 'Knowledge' which now showed up in the top right corner.

About the "well known" 'tactical battle hangs during enemy/AI phase' bug: It still happens in 2.4 - seen several times. And it probably is caused by AI units blocking (being in the way in some manner though I am unsure about the exact requirements) other AI units. There is one tactical map where it happens frequently but it can happen on others too.

Well, v.2.4 brings me only pain so far. I witnessed the infamous 'save corruption' bug exactly in 2.4 for the first time and now it breaks my every try: circa 80-90th turn game starts to corrupt save slots and throws me to desktop with memory error.

No mean can still prevent it: no swap file increasing, no DEP prevention, no tricky '4Gb memory' patch, no manual deleting of old saves and trying to save into empty slots.