As it usually is the case, the iFixit site is one of the first and probably the bravest to check out the insides of the new iPhone 5S that apparently has no obvious magic M7 chip or any other significant improvements, other than battery and, obviously, the new A7 chip and gave it a 6/10 repairability score.
Since the appearance of the new iPhone 5S is pretty much the same as the iPhone 5, the disassembly process is quite similar as well. Only drawback is the separation of the screen since it is connected to the new Touch ID home button via cable. Battery has been upgraded from 1440mAh to 1560mAh and iFixit notes that the device most likely has 1GB of RAM. Unfortunately, iFixit was not able to track down the "magic" M7 coprocessor that should measure motion data and despite the fact that Apple gave an impression that is is a separate component, it might be a part of the A7 SoC.
The new iPhone 5S also does not support the new 802.11ac WiFi standard since it is equipped with Broadcom BCM4334 based chip. As noted, iFixit gave it a 6 out of 10 repairability score which is not that bad but not good either.
Source:
iFixit.com.