Spell checkers certainly help and MS Word's grammar checker is fairly good.
I often have problems with the homophones too.

I also tend to drop letters as I type.

I think there are a lot more people with some form of dyslexia than we recognize. I think that we generally fail to recognize the milder forms. Often I notice people who drop letters and get them in the wrong order but correct for it quickly.
I am not talking about typos either.

From what I have seen most forms of dyslexia seem to affect the highly intelligent more than the average person too. Why that happens I don't know and can't even make a guess at.

I happen to know a woman who is mildly dyslexic and is a technical writer. I could joke about that being why so many manuals so hard to make sense of, but she writes very clearly because she has had to proof read her own writing all of her life.
It is a constant habit with her.