Yeah, I had a bit of a stutter and speech problems (I went to speech therapy for years, and I still say things wrong. I have trouble with properly saying r, w, d, th,and my -ed comes out like -it. I have to really think about tongue placement when I speak. It's quite noticeable, and it's definitely not
just my New England accent). I really think part of my speech problems though is caused from some sort of brain trauma. When I was only a few days old, I got punched on the head. I have a dent in my skull in the spot where I was punched. I ended up having a seizure problem afterwards that lasted a few years, and now sometimes I get bad headaches where I start seeing crap and I forget things easily (though,those last two could be from the 11 or so concussions I've had).
Like others above, I am also somewhat ambidextrous. I started out right-handed then moved over to left (left-handed wasn't natural, I
taught myself to be left-handed in kindergarten. Maybe I just wanted to be different?

<--which is something I think about, do I just want to be a guy to be someone other than myself?), my right handed writing doesn't look too bad even though I never write with my right-hand anymore, and certain things I do with my right hand only. Many things I do with both.
Though, it's common for cis-people to have speech problems too, or be ambidextrous. My older cis-sister stuttered really bad when she was a kid, my speech therapist actually said that my stutter was because I was copying her.

I think being trans would have more of an affect on our speech's tone, level, speed, stuff that makes you sound more like a guy or girl, rather than being a cause of speech impediments.