I did a test update of CU8 on the weekend and I did a next, next, next install of the updates because there was a couple of features I wanted to be able to test out.
I didn’t pay attention to two options that I didn’t need an that resulted in updating an external DLL which caused some compile problems when I got to the full compile before continuing with the update. By default there are two US Payroll components selected. I unchecked these and compile went through cleanly.
The compile errors will mostly show up in the PayrollTaxEngineUtil class and a couple of other associated classes.
Of course if you need US Payroll you might want to keep a watch on issue search or log a support case if this is blocking you.