If the Playstation 3 was a mobile console then perhaps making it lighter would be a good sales pitch, but seeing as they are hardly heavy as they are, and are meant to be stationary, it's not really exciting news.
As for them being slimmer, again, it's not that much of a big deal, I do not imagine most people would struggle to fit a PS3 in their homes as they are, not in such a way that it being slightly slimmer would make a drastic difference.
The only people who would benefit from this would be new customers, but to be honest they could get a decent sized PS3 for cheaper anyway, so again, it's not that great.
As for them being slimmer, again, it's not that much of a big deal, I do not imagine most people would struggle to fit a PS3 in their homes as they are, not in such a way that it being slightly slimmer would make a drastic difference.
The only people who would benefit from this would be new customers, but to be honest they could get a decent sized PS3 for cheaper anyway, so again, it's not that great.