At this time I'm seeing some reports of issues with JetPack and WordPress 4.6, as well as some issues with fonts on the front-end (your website). This WordPress update only changes the fonts in the admin area (back-end) to use system fonts, fonts already installed on your computer or device, making the admin area display faster, so it's unclear why several different users are reporting fonts are displaying differently on the front-end.
This doesn't mean there's anything "wrong" with this version of WordPress, but again this is a major release. A major release is meant to introduce new features which may also introduce new bugs. Sometimes it takes a few days or even weeks for all your plugins to be compatible with a new release. Check with each one of your plugins to verify they are compatible before upgrading a major version.
Since this version doesn't contain any security patches, my recommendation is to wait a few days, test the new version on a test site and make sure all your plugins still work.
NOTE: "Waiting a few days" means exactly that.
It does NOT mean "put off the update indefinitely, or just forget about it."
You should always keep your WordPress core, plugins and themes up-to-date.
We strongly recommend you re-read our WordPress upgrade guide and follow the recommendations.
Minor releases should be applied automatically or as soon as possible; they won't "break" anything.
Major releases should be applied manually, after being tested on a development site and all plugins checked for compatibility. A major release could possibly break something, which is why you need to test first.
Themes and plugins should be manually updated, after testing and checked for compatibility.
If all of this is confusing and seems like too much work (it can be and it is), check out our WordPress Update Service. For only $25 a month we'll take care of all your WordPress updating headaches, and provide you with an ongoing list of what's been updated and when, in case you notice any issues after an update. We also create a test site to test any plugins and themes for compatibility before updating on your live site, so there's never any surprises.