after all we are all human *beans* says kat.
I wouldn't bet on it myself.
My screen spelling used to be diabolical. I have no difficulty in spelling, but my fingers stray, and somehow on the screen my eyes don't pick up the typos. But then I found a little spellchecker that works with writing posts, and it makes life a lot easier for anybody trying to read what I've written - and it spots any Upper Case letters I've missed as well, or inappropriately put in.
I don't find it any quicker to leave out capitals letters. I suppose if I only had one hand I might, but typing with two fingers, one on each hand it is just as quick. After all, you can only put in one letter at a time, and whether it is upper case or lower case makes no difference to that.