The short of it: An Adventure in Time and Space was pretty darn good. There were problems, but it was good.
Bringing back the very beginnings of the series for the Nu Who fans who are generally ignorant of what was what back in the old days was a marvellous idea. Mind you, I don't blame the Nu Who fans for their ignorance, I just don't understand why so many of them have not even tried to get informed about it. Anywho.
For the most part, the movie was sweet and emotional, without being sappy and the performances were excellent. David Bradley was extraordinary as Hartnell. He did something with his face muscles that made him look nearly indistinguishable from Hartnell. Lesley Manville as Heather Hartnell was as sweet and subtly smart as she was rumoured to be. Sasha Dhawan as Waris Hussein was endearing, but having never seen him in interview ever, I cannot judge the performance. Jessica Raine as Verity Lambert was a little but too tame for me. Lambert was known for being a marvellous bitch of a woman, but Raine played her as almost meek at times, which did not gel with what I remember seeing and hearing of her. Simply stating in dialogue she was "piss and vinegar" is not enough. As for Brian Cox as Sydney Newman, he was all wrong. Newman was Canadian and cultured. Cox played him with a grotesque American drawl and a wet cigar (though he did smoke cigars). Reece Shearsmith as Patrick Troughton, for all the five seconds we see him, was all wrong as well and the wig was inexcusable. The other characters were generally fine, not notable in any way, positively or negatively.
Mark Gatiss's scenario was generally strong. The difficulty was to show the birth of DW in context, while making it an engaging story and not a docudrama. The challenge was to make a movie about a show, but to have that story carried by the people around the show, not the show itself. This was generally a success. Using the Tardis chronometer as a means to indicate the passage of time was a good conceit. Using the cast photo shoots to indicate the changes in the series over time was also smart. Overall, where it not for Bradley, though, An Adventure in Time and space would have been much less interesting. He carries the whole thing. His presence makes the movie less disjointed than it inevitably would be. To stop the movie when Hartnell leaves DW was the only way to go. The movie also manages not to glorify the original Doctor Who creators; they are likeable but they are all very flawed, except for Hussein, who is shown as perfect. Being a gay, Iranian man in 1963, it would have been bad form to vilify him in any way considering he is shown as being discriminated against. This is also probably why Lambert is shown as more likeable than she actually was.
In short, An Adventure in Time and Space was touching and a good homage to the artisans that created Doctor Who all those years ago. Were is not for the extremely tacky silent appearance of Matt Smith as Eleven smiling knowingly at Hartnell (a barftastic scene if you ask me), I have rather little negative to say overall. Even the wrong bits felt right in the context of the movie, within the limits of what good movie making demands.
I will watch it again.