There is a forum thread at the moment over at Autodesk about a number of people reporting errors after installation. Might be worth a read if you are having similar problems.
Also, whilst many have made comment about 2018.3 only being a bug fix update, (full list can be found here) but the key component of the 2018.3 release is part of the new BIM 360 Design which Autodesk is calling the 'next generation of C4R'.
Release 2018.3 makes Revit 2018 compatible with BIM 360 Design as prior versions of 2018 doesn't have the code to communicate with the suite.
So if you're not in a position to update to 2019 yet, then it may be something you are interested in beyond the bug fixes. Although, do your reading first as existing C4R projects need to be converted, they aren't automatically readable with the new BIM 360 Design.
|Fancy colourful image courtesy of Autodesk|