Jag är ganska säker Apparition är mycket långsammare än ljushastighet. Det finns en passage i pris som tycks indikera att åtminstone några tiondelar av en sekund men möjligen sekunder passerar under en apparition. Detta är trollkarlens subjektiva tid, men jag tror att den är ungefär densamma som den externt observerade tiden.
Citat Halvblodsprins kapitel 4, när Harry Apparates sida-tillsammans med Dumbledore.
Harry felt Dumbledore's arm twist away from him and redoubled his grip: the next thing he knew, everything went black; he was being pressed very hard from all directions; he could not breathe, there were iron bands tightening around his chest; his eyeballs were being forced back into his head; his eardrums were being pushed deeper into his skull, and then–
He gulped great lungfuls of cold night air and opened his streaming eyes. He felt as though he had just been forced through a very tight rubber tube. […]
(Portnycklar verkar fungera på samma sätt, eftersom böckerna pratar om liknande känslor när guiderna reser med dem.)
Uppdatering: Jag hittade ett mer relevant citat, i Order of the Phoenix kapitel 6.
Harry knew that Apparating was very difficult; it meant disappearing from one place and re-appearing almost instantly in another.
Jag tar detta som bevis på att Apparition är snabb, men inte så snabb som ljusets hastighet.