Clear Cache
Disable Plugin
Clear your browser cache (FF, chrome, ie)
uninstall
Remove files added by W3TC in wp-content (I always keep backup of the default htaccess file just in case)
Optimize/repair database
Install new version
Should be fine. I checked the changelog (always do so) and there were just too many things changed. Installing “clean” is safer in these situations I feel
I have no complex setup, I just use Browser and Page cache, and I think most will be fine.
Just remember, that a plugin that messes with your htaccess file and controls the way the pages are served to your visitors is not like any other plugin.
No one can predict conflicts or incompatibilities with setups. If you have a complex setup, it’s always good to keep a test site, where you can test all new plugin version before updating.
If you don’t want any unpleasant surprises with your production site, just take precautions and BACKUPS…
I use duplicator plugin for these things