Update to Oreo last night too, after disable SIM 1 (SingTel) immediate go update from Digi SIM card (Roam with Starhub).
So far here are my experience till now.
1. Samsung Health app pause step counting when the phone screen is off thought it still run backgroup, could be due to the Oreo power management.
2. Via and XBrowser unable load any webpage, uninstall and use Samsung browser since it can use Adblock extension
3. Android Pay is working, use it at Giant this evening
4. 3 Banking app DBS, UOB and Citi Bank is working
5. No problem with Mobile app to unlock bike.
6. Simple Pro for Fackbook cannot open.
7. Messenger that working for me - Whatapps, Wechat, Telegram
8. On Wechat problem with not able load subscription accounts content, likely same issue with loading page as Via and XBrowser, not big issue just another step using open with browser.
Too early to tell improvement of battery life.