When asked for his architecture of preference Linus quickly responded that “x86 is still the one I favor most and that is because of the PC. The infrastructure is there, and it is open in a way no other architecture is. The instruction set and the core of the CPU is not very important. It is a factor people kind of fixate on but it does not matter in the end. What matters is the infrastructure around the instruction set. x86 does have it and has it at a lot of levels.”
Torvalds did compliment ARM's hardware for mobile, but ultimately said that he had been "disappointed in ARM" because "as a hardware platform it is still not very pleasant to deal with. It does not have the same unified models around the instruction set as we do in the PC space, but it is getting better. Being compatible just wasn't as big a deal in the ARM ecosystem as it was in the x86 system”.
Compatibility is at the heart of chip manufacturing, but Torvalds in the interview voiced the fundamental problem of hardware vendors not having an incentive to create products to make a platform more useful.
Source: PCR online biz.