Not so bad
Those of you who have not been using any *UX OSs other than RHEL 6 and similar, will probably see RHEL 7 as a major departure and a pain in the behind. However, if you have A) been using and updating Fedora as well (that's had systemd and gnome-shell for ages) and B) Have also been using crusty ancient commercial *UX platforms (particularly AIX) are likely to see RHEL 7 as a minor step away from RHEL 6 and the differences to be trivial.
I do understand the theological issues with systemd and others that have departed from the usual *UX standards. It is a crying shame that systemd, for example, has now consumed a bunch of other perfectly functional packages and seems to be just getting bigger and bigger.
However, once you have got the hang of how systemctl works, it does just work. I do have to say that dumping the use of startup shell scripts and moving to a config file that contains the settings necessary and can parallelise the startup, is a good thing (tm).
I guess .. Bear With It .. is the best advice I can give.