If by x-factor you mean the factor that made PS3 sell below what it should have then yes. Blu-ray is something that is mostly unnecessary for gamers right now and it increased the PS3's price. The only examples of multi-dvd games on 360 are JRPG with a large amount of cutscenes. And last time I checked when I was playing Lost Oddyssey switching disks was the least of my worries (oh noes I have been playing for 15 hours and now I need to switch disks, dam my lack of blu-ray). You refer to mocking the 360's dvd capacity, well I recall people mocking the fact that out of 40 gigs of data on Heavenly Swords about 29 were uncompressed audio files which would make the difference only to people with several thousand dollars audio systems.
Bottom line: blu-ray is nice but not necessary yet. When PCs start using it then I will agree that it is becoming necessary since PCs tend to adopt all technologies first.
Not only that, current Blu-ray players are half the price of the PS3 so now that the format is taking off, PS3 will not be getting the benefit of this success but still paying the bill. Yes, if there is a gamer that wants to watch movies then the PS3 is a great choice but at least in my personal experience there is not a huge overlap between these two audiences. So once again PS3 was used to pave the way for the blu-ray but as a gamer I could care less, I would have rather had a cheaper/better system than a system that can play a video format I could care less about.
Proud owner of the following gaming devices:
PC, XBox 360, Wii, PS2, DS, PS3
