It seems that the IGN article may not have been so wrong after all.
An update on the BD-ROM physical format: (thanks to Quaz51 at B3D)
It appears (not confirmed) that the physical transfer speed of Blu-Ray may have been misinterpreted by folks:
http://www.blu-raydisc.com/assets/d...physicalformatspecifications_jan05b-12909.pdf
Reference velocity (1X) 4.917 m/s
Linear velocity: 7.367 m/s (Movie application)
User data transfer rate: 53.948 Mbit/s (Movie application)
In BD-Movie applications a BD player rotates discs 1.5 times the reference linear velocity of the BD-ROM
So, if the reading by the poster is correct (and it seems that way), then a 1x BD-ROM is only 36Mbps. The 54Mbps is specifically reference relative to the movie application as requiring 1.5x the rotational velocity of the BD-ROM reference.
So, if the PS3 only has a 2x BD-ROM drive, then we may only get 72Mbps as opposed to 108Mbps. Unless, somehow they continue with the rotational increase for BD-ROM even at the 2x level (which would essentially be 3x for read). Not entirely impossible, but the 54Mbps looks like an exception the format likely needed to be able to process 1080p video at an acceptable rate.
I think it's reasonable to assume that all read applications should be able to work at 54Mbps as I can't specifically think of a reason why movie data should be the only data that can be read at 1.5Mbps. However, a 2x drive, might only net you 72Mbps.
All somewhat confusing at this point, but it could set up a bit of disappointment for disc transfer speed.