alt Hacker NewsDepends a LOT on the res.
E.x. notebookcheck indicates that FEAR (released a yearish later) could get 20-30ish FPS at 640x480 but chokes at 1024x768 (at numbers matching the HL2 lost coast demo slideshow at 1024x768).
Gotta remember a lot of mac people were just happy to play something more modern than Marathon or Giants CK
There were also MacBook Pro models with dedicated GPUs that were capable of running HL2 decently. The 2006 MacBook Pro 15-inch had a 32-bit only Yonah Core Duo and a Mobility Radeon X1600.
I got my gaming start on one such machine - the Mobility Radeon was fine for HL2/Portal at 1024x768. Good memories.