This is very interesting as Sony really needs this one to pay off or they're going to be in serious trouble here. They've been struggling to rake in a profit for some time now unfortunately and it naturally costs loads more to product the PS3 than it actually sells for. Blueray is definately a gamble as if it doesn't become the movie format of choice half the reason it's there is now taken away.
Blueray defintely has the storage advange compared to HD DVD, read 25/50GB (single and dual layer) compared to 15/30. The 360 will have an HD DVD attachment as an option but it is not used for games, just movies. So the PS3 looks good as a forward thinking console in this respect. Resistence: Fall of Man, one of PS3's top games takes up 22GB's right now, you couldn't fit that on a single layer HD DVD, let alone a dual layer standard DVD. What do you suspect it'll be like in 3 years? Games only grow in size after all. That space is definately going to be a godsend for developers hopeing to build expansive worlds, save money by loading all the languages onto a single disk, offer hours of cinematics, fmv, high quality voiceovers, massive textures etc. I'm a pretty big 360 fan but I can't help but be very excited about all this.
As for Sony changing major specs that's a bit of an exageration. The core specs are the same, the system is just as powerful as ever. 1st year games aren't going to look a whole lot better than currect 360 games, probably worse than some, but compaired to the 360's launch titles we should see a good improvement that will become more pronounced as developers grow more accustomed with the tools they have to work with and the nuances of the system. So at the end of it's life span I belive we should see a decent gap between to two.
To save money Sony left out an Extra HDMI and ethernet port on the $600, and cut the card reader, HDMI port, and built-in wireless for the $500 model. That may sound fairly drastic but you can easily hook up any existing periperals you have to make up for those losses on the $500 model. You won't have an HDMI port but you can still do 1080p with component.
The motion sensing controller is a natural progression, it should add a new layer to games and give multiplatform games a few distinguishing features. I'm a bit ripped they don't have vibration any more but you can't have everything I guess.
The thing that really give me the most confidence though is the dedicated fan base, as others have said the PS2 sold way more units than the GC or Xbox 1 despite being a less powerful system. There are a ton of faithful developers, standout exclusives, and eager fan base to keep them in the running. The only thing that worries me is the price of games, $50 was bad enough but $60 is terrible concidering a lot of those games loose their fun factor after the first or second playthough, if that.