At first glance I thought they were merely continuing the dragon knights versus lion knights. But it looks like they've revived the black falcons.
The first image seems to be slightly misleading. If you read the comments, there is a suggestion about combining two copies of the set, and that appears to be what the first image demonstrates.
However it is a very attractive set regardless. The large gate reminds me of the porta negra in Trier (http://en.wikipedia.org/wiki/Porta_Nigra
), or the gate house to Lorshe Abbey in Germany (http://en.wikipedia.org/wiki/Lorsch_Abbey
). This is really stepping out from the typical square castles or tower-type forts which seem to have made up most of the castle designs over the years. The first photograph with two sets together looks so attractive, I almost think that lego should have created the set that way, and done away with the small peripheral structures. But perhaps they're trying to achieve a middle ground -- Maybe the thinking is that kids (possibly having less pocket money) will enjoy all the play features more and won't be too concerned with the open back to the gatehouse; While AFOLs, on the other hand, might enjoy a more complete architectural structure, and also having more spare cash, would be more likely to pick up two copies of the set. ...just speculating here, I'm probably way off target.
But I think that both this set, and the Mill Village Raid are clearly well thought-out efforts by TLG responding directly to a lot of the comments and wishes expressed here and elsewhere by their fans. Thank you, Lego.