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.
Definitely wasn't like that for Red Hat. We had a CFO with an IBM past which was a really nice guy and never ever felt like he was parachutes from IBM.
Now after 6 years legal, HR and finance will move to IBM starting next January; but my perspective from engineering is that after the acquisition it's been and remains business as usual.
I have no idea how it was for Hashicorp.