I tried out r503 last night on Win8 with my QHY5L-IIc (connected using "QHY 5L-II" driver) and my EQ6 (connected using "ASCOM Telescope Chooser"->"EQMOD...") and it all worked fine.
I didn't notice any difference in the quality of the guiding but I think I'll be staying with PHD2 from now on as there were a few things I found nicer than normal PHD.
