I just picked up a 128 Gb 6 Plus and was worried it would have 8.1.3 already installed but it came with 8.1.2 so I was happy!
Mostly I could get by without Jailbreak now, except for a few things that drive me nuts.
1) Ability to hide icons of apps I dont use (or dont use very often) like the Stocks app, Tips, Mail app (I use GMail), Safari (I use Chrome) etc. I hate having to put them on a page 3 or 4 of folders etc to try and hide them all.
2) Renaming app icons. Some Devs don't know how to name their app so some apps have names too long to display and end up truncated with ... after the name. Annoying! I use Icon renamer to fix the names to something much shorter!
3) I size the icons smaller. They always look too big to me stock. I usually resize to about 90%
Really if Apple included these abilities I would no longer need to JB. But the ability to hide icons on the home screen has been available in other OS's for a very long time and Apple has never decided to include it, so I think they dont want us to be able to hide them. They should make apps like stocks and tips etc able to be deleted (and able to be re-downloaded if needed from app store) that would be much better! Allowing us to remove them and gain space... not that I need it now with 128 Gb.