I too have the 17-70 C but no dock. It's a superb lens, big improvement over the kit 18-55. I find its focus accuracy and speed much better, it's much sharper (when discussed correctly) and on my d5100 at least it produced better colour clarity.
Definitely gets my vote. It's my go to lens of choice. In fact my 35mm f1.8 Dx hasn't had a look in since getting the 17-70 and we all know how great a lens that one is.