Let's keep this in perspective: The fingerprint reader was intended as a "more convenient way to unlock your phone" than a passcode.
For me, personally, this means that I can switch to using a serious passcode, and using my finger 99% of the time.
Unfortunately, the fingerprint reader was not quite as secure as Apple's claim -- IF you have a really good fingerprint of the correct finger, it's POSSIBLE but not EASY to trick the reader. (And of course, people will argue about how EASY it is, but I'll argue that mere possession of the phone is not enough -- there's almost certainly not "good enough" fingerprints to steal on the phone itself.)
To me, personally, this does not change its value as a "convenience factor". After all, if the fingerprint is not used for some time, it "expires" and then the thief has to crack the passcode.
However, Apple also wants people to use a fingerprint to authorize iTunes purchases. I won't be doing that, partially because IF someone can fake my finger, they MIGHT be able to steal hundreds of dollars from me. But more importantly, I don't buy that much STUFF from iTunes, so I'm happy to stick with a passcode.
The next question is, "Is the fingerprint data accessible?" and the answer is, "Probably it's harder to get the data out of the 'secure enclave' than it is to get a good fingerprint via other means."