You might be interested to know you can now buy Stealing Light from Waterstones as an ebook. It's also available direct from Pan Macmillan as part of a 3 for 2 offer that also includes China Mieville, John Scalzi, Neal Asher and Hal Duncan.
I should also add that I was recently contacted by the man in charge of taking Pan Macmillan deeper into the digital age as to whether I would be happy about Stealing Light being released as an ebook without any DRM; a request to which my reply was a hearty yes. Neither the Pan Macmillan site nor the relevant Waterstones page mentions this, unfortunately. It needs, I think, to be trumpeted; but the Waterstones ebook site, for one, is barely up. Let's see how it's looking in a couple days time.
Update: it turns out that all the ebooks available directly from Pan Macmillan at www.panmacmillan.com are free of DRM.