Here's a report of using CentOS 7 minimal from http://mirror.centos.org/altarch/7/isos/armhfp/ on a Raspberry Pi 3 Model B+.  tl;dr: I't does not boot.

So I just got a Raspberry Pi 3 Model B+.  I prepared an MiniSD card on a Raspberry Pi 3 (the previous) model and tried to boot the RPI B+ from that.  But it won't boot, the screen just shows the nice color spectrum.

If you have any hints or ideas, please let me know...

. mb