Testing has started to see if there is successful payroll parallel. Any specific points to consider?
Only test what you deem necessary starting with the critical components.
Sorry if that sounds a little simplistic. but a successful payroll has many parts, correct timecard entry, accurate staff compensation (all the way to the bank), correct recording in GL, accrual of benefits, Govt. reporting, management reporting, etc.
It sounds like you're running V10 on new hardware (Good! In place upgrades are definitely more complicated).
If you're asking if there are any specific components that were observed to be problem areas. . . (Recalling from dusty memory -- we did V8 to V9 to V10 in 4-5 year intervals) I think our biggest problem was keeping them in sync -- production (your V8) will be constantly changing vs the V10 will need to have all the same data updates in order for the reconciliation to agree.