yes well I have a few problems with the episode, but before I start that I want to talk about what the episode got right, that being the Doctor & the other Doctor, that was some really good drama, truly the best part of the episode.
However what I didnt like about the episode, well its got a few plot holes, just explaining how the Cybermen ended up their felt a bit weak to me, the fact any technology the Cybermen used may have come from the Daleks, the 10 Doctor montage was great, but where did the Daleks get that footage from in the first place?
now up to the point where Mrs Hartigan takes control of the Cybermen I can put the plot holes aside, but after that, im just wondering WTF and where exactly this episode is headed. Soon after this I am treated to the 100ft "Shinning Darkeness" Cyberman, and at this point I had pretty much given up on this episode (like I did with the Transformers movie, when the robots play hide & seek in the garden)
also I try not to mention this in reviews too much, but their was some poor CGI in this, the Cybershades claiming the wall being a good example.
In conclusion the episode got it half right, the Tennant/Morrisey stuff good, the Cyberman stuff bad, VERY bad. In truth had they just include a bad guy with a less complicated back story, and not inculded a 100ft robot attacking Victorian London, the episode would have been much better.
It pains me to say I thought this was an awful episode, but it was, certainly the worst Christmas specail, and maybe one of bottom 5 newWho episodes ever, and ill forgive a show I love alot.