How science works
A good fossil cuts through a lot of scientific argument.Scientists knew when the transition probably occurred, knew where the fossils probably where (where it happened) and what the thing would probably look like. Different people had different ideas about the details, and they went out and found the evidence to resolve the dispute. The different camps still talk to one another, and life moves on.
Other fossils had limbs that could have managed to push them around on land, but this has the same sorts of limbs that you and I have. The other limbs might have gone on to dominate the earth, but limbs like Tikaalik's did instead, and we're all here as a result.
I was about to write that this is entirely unsurprising, and I started reading Carl Zimmer's discussion of Tiktaalik, and he said the same thing:
It is no news at all, because it is just the sort of creature that one would predict from previously discovered fossils. Its place on our family tree has been cleared and waiting for some time now. And now it's filled.It's a fascinating picture of an ancestor of everything that walks on land, which makes it fully deserving of the red carpet treatment. On the other hand, it's exactly what we thought we'd find. It's a testament to all the science that came before it.