As long as you have CFW that's up to date, it's always perfectly safe and fine to update, no need to ask about it. Next time use the search though, such questions have been asked well over 300 times in separate threads already, no need to make more of them and if you don't want to do that, at least for simple things like this ask in the Noob Paradise thread...
Also, keep in mind that sometimes, when updating, certain homebrews will need to be updated as well since firmware updates may change memory addresses and whatnot. If you use NTR and other apps that will stop working once you get 11.9, make sure to update them to latest version as well, anything that works with 11.8 works with 11.9 as well, but from 11.7 to 11.8 some stuff changed.