Sounds incredibly interesting to me.
As someone already mentioned, this is most appealing for things like getting a cheap mini or ibook with a single processor and getting a cheap upgrade to a duo. Also, down the road there will be faster chips and cheaper prices on them. Right now, upgrading a brand new machine makes zero sense, but in a year if you can get a 2.5 gig chip for $150? That's a killer upgrade for dirt cheap.
Anyone know if the core solo and core duo are socket compatible?
It's on the motherboard. The processor is identical to the ones in PC's. It would be cost prohibitive to actually customize the CPU.