Not Dentin, but since I gave the same answer above I figured I'd weigh in here.

you expect one or the other, right? In other words, you don't expect to experience both futures, correct?

I expect to experience both futures, but not simultaneously.

Somewhat similarly, if you show me a Necker cube, do I expect to see a cube whose front face points down and to the left? Or a cube whose front face points up and to the right? Well, I expect to see both. But I don't expect to see both at once... I'm not capable of that.

(Of course, the two situations are not the same. I can switch between views of a Necker cube, whereas after the duplication there are two mes each tied to their own body.)

what if the replicator on Mars gets stuck [..] What is your probability of staying on Earth now?

I will stay on Earth, with a probability that doesn't change.
I will also appear repeatedly on Mars.

doesn't it seem odd that you are assigning any probability that after a non-invasive scan, and while your brain and body continues to operate just fine on Earth, you suddenly find yourself on Mars,

Well, sure, in the real world it seems very odd to take this possibility seriously. And, indeed, it never seems to happen, so I don't take it seriously... I don't in fact expect to wake up on Mars.

But in the hypothetical you've constructed, it doesn't seem odd at all... that's what a nondestructive teleporter does.

and someone else takes over your life on Earth?

(shrug) In ten minutes, someone will take over my life on Earth. They will resemble me extremely closely, though there will be some small differences. I, as I am now, will no longer exist. This is the normal, ordinary course of events; it has always been like this.

I'm comfortable describing that person as me, and I'm comfortable describing the person I was ten minutes ago as me, so I'm comfortable saying that I continue to exist throughout that 20-minute period. I expect me in 10 minutes to be comfortable describing me as him.

If in the course of those ten minutes, I am nondestructively teleported to Mars, someone will still take over my life on Earth. Someone else, also very similar but not identical, will take over my life on Mars. I'm comfortable describing all of us as me. I expect both of me in 10 minutes to be comfortable describing me as them.

That certainly seems odd, but again, what's odd about it is the nondestructively teleported to Mars part, which the thought experiment presupposes.

What is the mechanism by which you expect your subjective experience to be transferred from Earth to Mars?

It will travel along with my body, via whatever mechanism allows that to be transferred. (Much as my subjective experience travels along with my body when I drive a car or fly cross-country.)

It would be odd if it did anything else.