Each language feels different when it hits your ear, and feels strange as it exits your mouth — often leaving your tongue twisted into a new, uncomfortable shape! But one other difference that might not be so obvious is the way it "feels" to type in that language.
I'm a touch-typist. I've grown up with computers. I had typing class in first grade. I type fast and I don't look. And I expect that a lot of people in my generation or younger fit that description.
Interestingly, it seems that we all develop little idiosyncrasies in our typing. I've known people who type extremely fast, but who only use the first two fingers on each hand. And I'm sure we've all seen how one hand gets going faster than the other and you end up with misspelled words like "teh".
I noticed long ago that when I type the letters IN, my finger naturally wants to add a G, and this often leads to typos like "thing" when I meant to type "think", or "whinge" when I meant to type "whine".
Cheating in Italian is relaxing
But I also notice interesting idiosyncrasies in other languages. For instance, if you look at the "home row", four of the five vowels are actually one row up, which isn't such a big deal in a consonant-heavy language like English, but can be really inconvenient in vowel-heavy languages like Italian.
I've noticed that since beginning to study Italian this year, my resting position on the keyboard has actually changed! My hands now naturally rest in such a way that my left hand covers "A-S-D-V" and my right hand covers "N-I-O-;". This isn't by design, of course. It has naturally evolved. But it makes a lot of sense: the letters F, J, and K are almost unused in Italian, and the L isn't nearly as useful as the O. With my hands in this position, I can type "che cosa" almost without moving my hands at all.
I've also found that I can find "option+`" without looking, and when I do, my left hand naturally returns, not to the A+S+D+V that I mentioned above, but to A+W+E+F. No doubt this is because of the natural motion of typing a vowel immediately after typing that modifier for the accent. With my hands in that position, I can type à, è, ì, ò, ù, all easily and without looking.
I can't help noticing that, when comparing English and Italian with regard to had fatigue, I actually feel much more natural and comfortable typing in Italian — even in spite of the fact that I've been touch-typing in English for almost 30 years and Italian for less than one.
The same is not true for me, however, in Spanish or Russian. In Spanish, I find that the modifier keys for accents and tildes are too much of an interruption to my typing. I never really developed any ability to type quickly in Spanish. But I can, however, type pretty fast in Russian.
Russian is painful
One can immediately recognize that Russian is a very consonant-heavy language by the fact that the most important vowels are the hardest to reach from the "home row". In fact, it seems like several of the most important letters are those in the middle. I wonder if Russian typing classes teach a completely different technique, because the "home-row" style of touch typing is horribly inefficient.
I find with Russian that I begin to resort to a three-finger modification of that two-finger method I referred to above. My hands actually start to hover above the keyboard, not actually touching the keys at all.
And because all the best letters are where it's hardest for me to reach, I make a lot of typos with them. For example, to type the word принтер (printer), you would type GHBYNTH on a standard keyboard. Try doing that quickly without making a mistake!
Speaking of Russian, here's a fun little rhyme that Russian children learn in school:
Мы писали, мы писали. Наши пальчики устали.
Мы немного отдохнём. И опять писать начнём!
It says, "We've been writing, we've been writing, and our fingers are tired. We'll take a little break, and then start writing again." Of course it's more fun in Russian because it rhymes. I learned it, of course, after complaining to someone about how my hands hurt when I type in Russian.