Loved this game.
Note that my opinion is untainted by the original Ego Draconis. I bought DKS just before Christmas last year, and happily played it all the way through. I can see how the original Ego Draconis could be viewed to have a frustrating ending, but the expansion plays very much like a welcome 3rd Act, and together, it all forms a very satisfying story and game experience.
I know there's lots of griping about the gameplay as a dragon, but I found these to be overblown to my personal taste. For one thing, once you gain your dragon form, there's TONS of gameplay remaining in your human form. I kind of liked the way they had you exploring the world in dragon form, then entering the dungeons/caves in human form. I think adding a 3rd dimension to the world exploration added a lot, and it was executed very well in the Fjords.
Of course, there's dragon combat against the numerous towers and ballistas, and while I'm not sure this could be categorized as 'fun', I didn't find it particularly challenging, either (especially when I got the hang of using the right mouse button to give a burst to my movement in any direction every 1 second). If anything, it got a bit repetitive. I admit that I experienced some of the same feeling going into each commander's floating citadel realm as I had going into each of the Oblivion gates ("well, here we go again"), so there were a few hours in the middle of the game that dragged a bit.
On the plus side, you were rewarded for these efforts with phat loot in the form of set pieces, and it was always enough to pull me along. And again, this one average part of the game is outshone by the 90% of it that's really top-notch IMO (that's including the expansion/3rd Act that takes place almost entirely in human form).
If I were to use one word to describe this game, I think I would use 'Bold'. From the opening cutscene featuring a floating warship, to the interesting (though expected) plot twist that takes place very early on and turns your friends into enemies, to awarding a player their own fortress, to the big risk of allowing you to play and develop as a dragon, to the 2nd Act ending that will leave you saying, "WTF? Those bastards!"……the whole thing stroked my love for high fantasy in all the right ways and left me very satisfied.
I didn't finish it before the poll at the end of last year, but this easily gets my vote as RPG of the year for 2010. So glad the Devs went back and re-worked this and re-released it as a complete game, because in its current form it shines very bright…