UPDATE
Apple issued an apology Wednesday and provided a temporary workaround for iPhone users who updated to iOS 8.0.1 and lost the ability to use cellular service or the Touch ID fingerprint sensor.
In an article posted to the company's support site Wednesday evening, Apple offered step-by-step instructions showing customers how to restore an iPhone to iOS 8.0 using iTunes.
The company also said it is preparing a fix in iOS 8.0.2 and will release it "as soon as it's ready" in the next few days.
"We apologize for the great inconvenience experienced by users, and are working around the clock to prepare iOS 8.0.2 with a fix for the issue," an Apple spokesperson told re/code. Sept. 25, 2014, at 7:46 a.m.

UPDATE
Apple has pulled its 8.0.1 update. Sept. 24, 2014, at 10:00 p.m.
There's a new update out for iOS 8 and it's causing some slight problems for iPhone users - namely, disabling their ability to connect to cellular service.
Jeff Vreeland@jvreelandFollow
Just updated my iPhone 6 to 8.0.1 and now both my cell service (AT&T) and Touch ID are not working.
8:39 PM - 24 Sep 14
Scott@swb1192Follow
The early (but unconfirmed by Apple) reports seem to suggest it's an iPhone 6 problem:
Andrew Cunningham@AndrewWritesFollow
Anyone with a 5S install the 8.0.1 update? Any problems? Consensus seems to be that it's an iPhone 6 thing.
But still, you might want to wait for a bit to head over and update your iPhone/iPad/iTouch operating system to the newest iteration of iOS 8.