I was lucky enough to see a talk by one of the authors recently and was left very impressed. Quantum computing is probably the 'sexiest' application of ultra-pure silicon-28 but there are so many others besides, including being able to use ultra-fine optical transitions to identify defect complexes within the silicon (arrangements of impurity atoms that can influence the properties of silicon-based devices). If I remember rightly, there were several defects that had been misidentified for years based on entirely reasonable Occam's-razor like reasoning that have now been correctly identified thanks to this work.
[1] http://news.ycombinator.com/item?id=6617183
[2] http://www.sciencemag.org/content/336/6086/1280.full.pdf
To illustrate what I mean, consider the fact that the Czochralski process [1] exists and that it means you can get huge, pure, relatively defect-free ingots of silicon (see [2]). With new materials, we're happy just to grow a few microns of the stuff, let alone something like that.
So you're right, silicon really is very incredible :) but we've reached the point now that the new innovations are in part possible by sheer momentum alone, like the billions of dollars of investment you mention. The big challenge is to develop new materials that initially (possibly for decades or more) are inferior to silicon but might ultimately unseat it. The only problem is that no one really knows what that material will be in advance. A lot of people right now are gambling on graphene, and from the amount of investment alone something interesting should come from it, but who knows if there's something else better out there just waiting for the attention it needs.
[1] http://en.wikipedia.org/wiki/Czochralski_process [2] http://en.wikipedia.org/wiki/File:Monokristalines_Silizium_f...
Logical qubits are made up of many physical qubits, with relatively short life times, to make one logical qubits with an infinite life time. The longer life time of logical qubits makes it considerably easier to perform long calculations and store information.
If anyone knows how easily quantum error correction can be applied to this system I would be interested in finding out.
Single qubit operations have been shown to be on the order of 10's of microseconds for P nuclear spins in Si. (Unfortunately behind paywall, http://www.nature.com/nature/journal/v496/n7445/full/nature1...)
[1] Quite enjoyable fiction. My canonically chronological SG viewing order for maximum enjoyment is available at https://docs.google.com/spreadsheet/pub?key=0AkwxWLA63pAmdG5...
