This set is awesome for a few reasons. First, and most importantly IMO, is the inclusion of this set as part of a series of sets from that time period that can all go together into one big castle, as Jojo shows in this gallery:
Isn't that exactly what the CCC standard is all about, making smaller units that all link up to make a huge combination? This set was cheap enough that you could get several to make your castle even larger.
Another fine point of this castle was that you got multiple figures from two different factions, so it was a great army builder, with attackers and defenders to give better playability.
The design of the siege tower is nice, and is a perfect blend between realism and Legoland design.
This set is also great for weaponry. According to Peeron there are 4 spears, two swords, the battle axe, two shields (including that round one--I don't have any of those
), four helms (of three different designs), and a bow and quiver. Awesome.
Perhaps I am alone in this, but I really dislike the castle wall panel piece. I know these are a way to build a big wall quickly, but the even rows of windows, the lack of the lines of bricks (which look realistic in a castle setting), and, most importantly, the lack of flexibility in design are all big negatives to me.
One minor thing, the wagon wheels are a great element (I just bought a bunch from Troy's shop), but they look too flimsy to support the tower. I prefer the 4x4 round bricks as wheels for larger things as seen in the Bulls Attack set.