I recently discovered this rpg quite by accident yesterday at my FLGS looking at board games. They had two copies of the 11th Doctor box set behind the counter, and when I asked about them, it turns out the store got them by accident as they were supposed to get the card game. After looking at the box, I realized I had to pick it up.
My daughter and I are currently catching up on the series on NetFlix, and are currently on Season 3 with the 10th Doctor. Because of this, we are shelving the box till we get caught up with the current Doctor. Looking through the box set, I am very impressed with the content, but would love to get 10th Doctor edition. If the rule sets are similar, would it be a waste to get the 10th Doctor box set?
You also get stats for some of the monsters from the 9th and 10th Doctors' series, plus a completely different Adventure Book. But unless you're a completist collector, it's probably still not worth the cost. You'd do better spending your money on the supplements - you'd get all the monsters stats (with the exception of the Reapers, I think) in the Aliens and Creatures set, and it costs less.
It really depends on how in a hurry you are to get 9th and 10th Doctor content, as mentioned above. Those particular sourcebooks are going to be coming out with that material sometime late this year or early next, so it may not seem as worthwhile.
I'd get the Time Traveller's Companion, instead, but then I'm biased a bit in that direction...