I'm with a company that was acquired by IBM ~2.5 years ago. The internal systems are definitely rough, but for the most part it's business as usual.

I've heard chatter from our engineering leadership that IBM is trying to push some silly initiatives, but we've been able to prioritize the right work so far.

I also get more equity (one time award + employee stock purchase plan) than I did previously, and with how IBM stock has been performing lately this has been a net positive for me.

FWIW I have heard that IBM used to force their management style on acquisitions in years past, so perhaps this is a fairly recent shift towards a less hands-on approach.