there are like 3 devs that don't like it because they are used to the github way of doing things, they always have the github tab open and prefer not to have notifications in slack.

We disabled pullpo for these people. However they can still collaborate with the people that use pullpo. The comments they send to github are brought to slack too and viceversa.

Still, code reviews take 2 to 3 times less

Yeah I did a bit of a deep dive on Pullpo - it looks great, small passionate team! I was curious if there is anything that you don't like about using it as part of your workflow? Like I can see your colleagues prefer a specifically different type of workflow - why did your team adopt it?

Most of the devs actually love it, and they have excellent customer support. I you suggest a feature, they'll probably do it.