I am very bullish on iOS 8, but I can't see why this isn't good advice. Unless you really want one of the features iOS 8 offers, or unless you're having trouble updating or installing apps that you want, if it's running well, leave it be.
I did that once with a 4S - it was on 5.something when all my other devices were on 7.1.2, and it got to be very frustrating. Every time I synced to update apps I'd get this list of three dozen apps that couldn't update because of the iOS version, and there were lots of apps that I couldn't install at all. But that was two full versions behind, not one.
For the _._.x releases I'd need to be told a damned good reason not to upgrade. The 3rd digit usually means critical bugs and security flaws were fixed and not much else. (Otherwise they'd just have waited until 8.2 to come out.)
Thus far I've not seen anyone give a good reason not to upgrade so my default advice would be "absolutely."
my dads 5S has been on 7.0.4 since we bought it for him a year ago. If I remember correctly that was the one SSL bug or something. Not one thing has happened to his phone security wise.