Basically, it's more of the same. The gang travels around in search for Sakura's feathers. However, this time they re-visit some of the "worlds" they went to in the first series, which shows how the situation they left behind has developed -- sometimes for the worse.
There is a lot more going on than in the first series. The plots seem to be a bit deeper than before: sometimes the bad guys from a previous episode also travel through the worlds, we get to see a lot about Kurogane's past, there is some time-travel under the direction of Yuko, and Sakura takes a much more active role. This is, in my opinion, a change for the better.
However, we still get lots of foreshadowing from the mysterious bad guys who never seem to do anything...
Visually, there haven't been any changes from the first series, and the music is still upto Kajiura's excellent standards.
If you liked the first series at all, you will like this even better. If not, then this second series is not going to change your mind.