Watched the 3d version on iplayer, complete with one-eyed logo.
It WAS a bit annoying, but I was able to tune it out after a while. More annoying was the flicker - there was a lot more than I'm used to with blu-rays. Don't know if the refresh rate was lower or something.
I struggled to actually watch the thing in 3D, despite having all the required tech. I was out at the weekend. I eventually found an obscure blog posted on the Friday suggesting how to record from Sky using the red button channel. Not useful to me as was away by then.
For some reason my (not as smart as they'd like to think) TV wasn't able to work out that it's own built in iPlayer app was trying to display some 3D content. Luckily my Blu-ray player also can talk to the internet, and I'd got iPlayer fired up on that I was able to get properly cross-eyed.
Perhaps all these things might suggest why few people have been watching BBC in 3D?
Oh yes, and the whole helicopter over London sequence. That was a bit pointless. I've since watched the episode in 2D, and can confirm that the helicopter shots looked better in 3D. But it didn't add anything to the plot, and wasn't really all that funny.
The paintings worked much better in 3D than 2D, and they were intrinsic to the plot, so thumbs up for them. As did the battle scenes, despite the non-movie-budget FX.