I just installed 5100 and opening ArchiCAD 18 took ~10 minutes to get to the Open dialogue. Opening the file itself took the normal time. Closed ArchiCAD and reopened in the normal amount of time to Open dialogue and the file. Not a smooth transition, but it works now.
No Teamwork/BIMServer set up in our office.
AC19-23 | Win10 Pro | i7-8700K | Quadro P600 | 500gb 960 EVO M2 | Dual 28" 4k Samsung U28E590