I've been following the project since it was first announced, and while it's interesting, I don't find it particularly useful... I mean, I got a laptop for its mobility, I knew I was sacrificing a bit of graphics performance (although these days the performance loss compared to desktops is unsubstantial). I also don't want a device bigger than my whole computer, with its own power source, sitting on my desk...

As for extending the life of old laptops, well, laptops get old and cheap so fast these days that it's not worth it - the difference between a Quadro FX 770M and FX 880M (which are what, 1-2 years apart), for example, is more than 50% in performance...