Good find, wxlt!

"Intel's Mark O Miller confirmed the quality issues to The Register, saying specifically that the first batch of modules didn't operate over the specified temperature range."

This is exactly the fundamental problem of silicon: the heat. Even if you didn't care about power consumption, it is the heat which must be removed from the chip fast enough in order to not burn it.

Here's were gallium arsenide excels: less power consumption, less heat. Besides from that, gallium arsenide has better optical properties than silicon anyway.