My update process from 1.8.3 was really smooth:
meteor update # the core to 1.9
meteor update --all-packages # all yet non-updated packages
rm -rf ./node_modules # remove modules
meteor npm outdated # check outdated npm packages
meteor npm install --save <...> # install all outdated
meteor # boom - it's running
No issues at all. I also had a very smooth update from 1.8.1 to 1.8.3 after all packages and npm modules were up to date.