Decompression in conjunction with primitive multi-tasking on MacOS and Windows. That remained an issue until Windows XP.

(Very small groups of) people used be in awe at LAN parties when I showed them how Linux could play an MP3 without stutters while copying large files across the network and browsing images.

Then it was time to play games and people were less impressed by me not being able to join any other game than Quake...