I take NAC daily. Can't say I notice much of anything one way or another.
This has been my experience as well.
I continue to take it because I've read it's helpful for your liver, and in the last few months I've been on Rifampin and Diflucan (at different times), both of which are hard on the liver.
When my ALT and AST went up, my LLMD specifically told me take NAC, Milk Thistle, Alpha Lipoic Acid, and Pekana Big 3. That seemed to bring my numbers back down.