I thought it was a nice, change of pace episode myself. It's always fun watching this Doctor interact with the modern world (since he does it so rarely), and the mystery surrounding the cubes was a good one. The moment where they all start behaving in strange and different ways was perfectly directed, I thought, and genuinely had me wondering "what the fuck is going on?!?"
And the creepy robot girl in the hospital was a nice touch too.
The only shame of it is, is that after such a great setup, the source of the invasion ends up being... just another alien ship in orbit. I would have loved something a lot less conventional than that, to go with the originality of the "slow invasion". But oh well. The Shakri alien was still sufficiently weird and creepy enough to get the job done.