Either there’s an internal bug; heavy end-user demand; slow throughout and/or problematic servers… whatever the case may be, a posted 5 hour update time for a file that is less 100mg harkens back to the dial-up, analog ‘net access! Clearly, Apple’s most recent release is not their finest hour…
PS: Okay, the actual iOS8 patch did not take 5 hours… Nevertheless, in this day and age, it seems odd that this was the initial timeframe provided.