That's true, the current Doctor is very good at humour, but can't bring across Tortured Soul at all well, it just doesn't really seem to suit the character.
As others have said, the story was really just a mechanism to hang some mysterious waiting, various nice ideas, and a variety of bad jokes off of.
I particularly liked that one of cubes played the Birdie Song on a loop, clearly intended to torture people.
I guess part of the problem with the current series, is that the stories can potentially be long and complicated enough to require more than one forty five minute show, so requires either a split across two episodes (which I personally find irritating), a longer Christmas Special (or similar), or end up being a bit abbreviated in places.
For this one, they basically removed a lot of the explanation of what was going on, in favour of a very rapid ending, which sort of tidied up many loose ends, although a bit inadequately to my mind. The Shakri may yet return, in a more concrete form, they seem to be a suitable not actually evil, but powerful race to get up to all sorts of cunning and mysterious things.
Even the title, the Power of Three, seemed a bit contrived, with not much basis in the end. Not as clever as some of the earlier titles. Using the Sonic Screwdriver to so trivially solve things was a bit of an over simplistic solution. The Sonic Screwdriver is a tool with not enough limitations, which is why you generally don't have stuff like that in Science Fiction, because it's too powerful and you're often left asking why it wasn't used this time. It's limitation against wood is a good example of how they provide a humorous limitation, which has been used to good joke effect in some episodes. In older series of Doctor Who, they have discontinued the sonic screwdrivers use altogether, because of this plot problem. Is there a term for this type of plot device? It's not really a Deus ex Machina, but it has similarities.
It's never really explained why the Shakri used such a half arsed approach, when even we can think of many much easier approaches to solve that particular problem. It may be novel, and a bit inexplicable, but that alone isn't the basis for a good plot device, it needs some internal consistency and logic.
Still, some good light-hearted moments, and as others have said, the return of a Lethbridge-Stewart, with a good line in banter. Hopefully she'll also be back (and I'd be surprised if she isn't because this story was clearly partly a way to introduce her to us).
I'd say something like 6½ out of 10. Not brilliant, not bad, and has some nice features. The return of the Weeping Angels next week could be very good, but lets hope they don't get too overused, we've had them in several episodes now, and good baddies should be kept to a minimum, least they become a bit of a cliché, and predictable. Blink was by far the best episode that they've been in, although The Time of Angels/Flesh and Stone wasn't half bad. An appearance by River Song is also rather good, since she always has good lines.
