I updated my s7 to Oreo as soon as it was availble - not issues at all. Much smoother and responsive then Nougat, and (as stated above) my battery life has improved a bit as well. Seems like they dealt with all the issues with bootloops that others experienced in other regions of the world during their rollout.
Lots of things have been working great - just some notification issues...and now that you mention battery life, I'm worried mine is worse. Oh well I will keep an eye on it
Yeah, notifications are different in Oreo as compared to previous versions.
For battery, assuming there's nothing obvious causing it you may want to back up as much as you can and then do a factory reset and start off nice and fresh.