I kind of liked it. I get what they were trying to do: have Hartnell realize that Doctor Who would become a very big thing, beyond him, and him imagining what The Doctor might look like in the far future. In the same way, it was Matt Smith looking back and being proud of Hartnell for laying the groundwork for everyone. It was like Smith appeared to say "Thanks William." Personally, I think it would've worked better if we had somehow seen all the Doctors, or at least a large number of them.Watched "An Adventure in Time and Space". It was okay. The bit at the end where Matt Smith shows up was a little weird and uneccessary.
One thing I didn't like was towards the end, when Hartnell cried, "I don't want to go." That's Tennant's line and should only be Tennant's. But I can't deny I teared up a little when he said it.