I personally could see plenty of uses for this thing. I haven't bothered installing Linux on my PS3 because I want to also be able to play games and I don't want a huge damn hassle all the time.
But so, with dual-boot I'd be able to quickly switch to either Linux or PS3, giving me best of the both worlds. I personally see PS3's multimedia capabilities as just plain freaking horrible, so booting it to Linux and having XMBC (or something similar) autostart at boot I'd have an amazing multimedia player and a great games console in the same package.
Of course, there's plenty of other uses for Linux and with proper dual-boot system in place one could really start designing a proper PS3-oriented distro, useable both with just the joypad and with a keyboard if you have one attached.
I definitely hope Kmeaw does indeed incorporate dual-boot, it's bound to bring up some nice Linux-oriented projects and developments and motivate people.
Playstation 3, Waninkoko V2, 1 terabyte internal HDD.