Early this month Fiksu reported that iOS 8 adoption is slower than the gains demonstrated by iOS 6 and 7 in their first weeks after launch. Apple launched iOS 8.1 (which adds Apple Pay and Continuity) and the good news is that version 8.x is now on over half of the devices.
The bad news is that Apple's developer page points to 52% adoption of the latest iOS branch, that's 13% or so more than three weeks ago. That's starting from just under 40% adoption after the first three weeks of availability, then at the iPad event Tim Cook announced the number had grown to 48%.
However, that was two weeks ago meaning iOS 8.x adoption grew only 2% a week since then. Over the next month it will become clear if people were just waiting for the 8.1 goodies or prefer not to update at all.
The botched 8.0.1 update certainly put some people off (it interfered with the fingerprint sensor and even mobile connectivity). That has since been fixed but the jump to iOS 8 still requires plenty of free storage – as much as 5GB, which is painful for those on 16GB devices. Apple's 2014 devices still start at 16GB, which is sure to be an issue when iOS 9 comes around.