You're right, of course. The thing about the points you, Joshua and Squilliam use is that they can't be argued against. Add 'controller preference' into the mix. They're all perfectly good reasons to favor one console over another. Essentially, if all your friends are on one console or you like the games more, you're already made your choice.
Which clearly isn't the situation in which the prospective owner hasn't chosen and is looking at two $299 consoles and is trying to figure out which looks like a better deal. In this case the feature list does matter. Are you saying this guy doesn't exist, that by now everyone's made their choice?
But as I said, "features" for consumers aren't, "technical check boxes." Does a "777Petaflops" really matter to the consumer? Of course not. Even BluRay isn't necessarily a black and white "check box" if looking at it from a consumer consumables and services perspective. As a consumer if I want video media I look at the consoles and have a number of options: the PS3 has a Bluray drive that plays BluRay movies, DVDs, and you have media on the PSN store. On the Xbox 360 you have a DVD drive, the Xbox Live library (which I hear is larger, if not higher profile), and of course exclusive direct Netflix support for movies (SD and some HD) and TV shows.
This is what I meant by a platform--it isn't about, "lets put all the features on a scale and measure it out." Similarly, for consumers who are primarily gamers, games are going to be a huge factor in deciding the platform's relevance. Having a larger back library of better games at cheaper prices counts for something for gamers who have heard of all the great games on the market but don't earn any.
Ironically I think consumers are still out of touch at times, even with PSN/Live. A gent at work has an Xbox and mentioned it in passing. I asked him what games he liked and he mentioned NCAA and FIFA and racing games. I said I liked sim racers and I was looking forward to the new Forza Motorsport--and he had no clue what that was.
I think we give consumers far too much credit for knowing all the details of the consoles, I think things come in more generalities. We still read people talking about PS3 versions of games being a lot better fr example--PR sticks. Just like bad PR sticks. But the eb and flow I think is closely tied to major products and events (e.g. the 360 snagged a huge amount of Madden gamers, benefited from the Halo buzz, hurt by the RRoD, etc).
At this point in its life the PS3 is going to be judged by the software and services it provides now, not any potential what ifs at $299 the software (games and movies) should be compelling to many, especially consumers who have held off. The question is how far can Sony make inroads in this economy before MS and Nintendo strike back with their own price and software moves.