Just heard it on NPR. From the apple.com homepage today:
Sad day. I thank Steve for enabling all these innovations that have made a profound difference on my life and that of millions of other people. A lot of what I do in my science work and my photography would not have been possible or would have been far harder and probably quite frustrating without them. Buying my first iPod (when they were still Mac only and the iTunes store didn't exist yet) made me rediscover my love of music. Steve was truly remarkable. The epitaph at the Apple site says it well. Also a worthwhile read is his 2005 Stanford commencement address.
Edit: A very good write-up by John Siracusa at ars. Mirrors my feelings quite well but John is actually a good writer.