I am considering (strongly) CBRN (Army) as my MOS when I enlist next month. Who can give me first hand experiences on AIT, assignments, etc?

I would look at a different MOS. Almost all of the 74D's that have worked for me and with me get stuck in the S3 shop doing everything but 74D work. The ones that get placed in a company or troop work in the orderly room, again not doing 74D work.

Kelsey Chlovechok if you are with a chemical unit you will receive great training and do your job. If you are stuck in another (any other type of unit) you will be the residential expert and be the one fitting everyone for a mask, doing inventory for the chemical equipment, and allegedly for officers you get stuck doing the USR (a report nobody likes to do). While most Commanders want everyone to do their job and train in their job it is especially hard when there are only 1 or 2 people of that MOS in the unit.

The question is do you feel so strongly that you want to learn CBRN that you are willing to risk not doing that job later on?

NOTE: All MOSs have some issues and all will eventually lead to staff time if you stay in long enough regardless if you stay enlisted or go officer.

Are you sure you want to be exposed to live chemical warfare agents? Your graduation requirement is handling nerve agent in AIT. So if that sounds appealing to you then get after it.