I am really enamored of Simplenote, a website / app that is like a giant folder of your own text files that effortlessly syncs across any device, whether it's an iOS device or a Windows machine or an Android thing or your Mac -- actually anywhere you can get to a browser, you don't even have to install anything to have access to your info. Compared to, say, Evernote, its "pure text" approach may feel a bit stripped down, but I love it. (I am reminded of the late-90s Computer Stew video Notepad Rap...N to the O to the T to the E, P to the A D E X E my Notepad!)
There's one quirk of its UI I hate though: if a line of text starts with a "-" or "*" and you press return, it assumes you're starting a simple list and so it puts a starting "-"or "*" on the next line. This bugs me: if I wanted to continue a list, it's pretty easy to type "-" again, and even though I can hit delete or return, the presumption irks me. Maybe it's just an iOS thing (though I thought I had seen it on the website at one point) because it takes an extra taps to get to the keyboard for those characters... But for an app that seems so firmly in the "do one thing, do it well" camp (pinning notes to the top of the list and tags are its only "frills") it's a bit jarring.
Similarly, one of the first things I look for in a code editor is "how hard is it to figure out where to turn off auto-match of ) and ' and [ etc?" -- i.e. you start typing a "(" and it automagically fills in the ")" and (hopefully) hops the cursor back to the middle. Some are smart enough so if you accidentally type the matching closing character, it erases the one it made, but still: I hate it, and turn it off as soon as I can figure out where, since the feature goes by different names in different editors.
I tried to figure out why it irks me so much, and I realize it's the inconsistency of the thing, when compared with all the other programs I use to enter text - most of them don't autolist or autocomplete or whatever, and so I can't just type - I have to keep in mind what the program I'm doing does. Inconsistency is horrible, even if it's in the context of other programs.
Bonus gripe: in general, I'm ok with autocorrect on touch devices, since it does a pretty good job of making up for the deficiencies of the input device. But, I hate the parallel autocorrect when I'm using a laptop keyboard, where typing is more accurate (but I like the underlines indicating I screwed up, especially since the interface for correcting that is so smooth as well - and some of them are fairly smart, hinting that maybe I made a grammatical typo, not just a character blurble.) ON THE OTHER HAND, I find iOS's insistence that capitalization is a part of spelling correction to be fascist. (I'm not talking about capitals at the start of sentences, which you can turn off.) I'm not saying I want to be e.e. cummings, but if I want to type star wars and not Star Wars I should have that option. And again, the inconsistency and general stupidity of the fixes irk terribly; if I write about my friends "amber and jim" Jim gets the capital, and Amber doesn't, simply because her name doubles as a common noun. Combine that with the general clunkiness of the correcting interface, and the way the shift-mode is sometimes "sticky"... blargh.