I somewhat agree (honestly, I found Brisingr very enjoyable, he began and finished it very well), but it was very necessary. It's because Paolini made a HUGE mistake during Eragon and Eldest by having him make too many promises to help too many people, and have too many responsibilities that no one really cares about. When he was making what would have been the last book, I guess he finally realized: "Oh crap. Eragon promised ten different people to do ten different things and now I have to make sure that he does all of that, or else the story will have many holes in it and I'll have to explain how Eragon still manages to have enough support against Galbatorix even though he broke all of his promises." And so Brisingr ended up serving as more of a bridge if anything. Honestly, I can only think of one other alternative that he would have had in that case, which would be to just come out and say in the very beginning: "So a year or two have passed since the battle over the Burning Plains, and Eragon has fulfilled all of his promises." Which would have made me, and I'm sure many other readers, facepalm themselves. As Iseris said, it's not about publicity in this case (well, it will always involve publicity at least slightly, as with nearly everything, but I don't believe that Christopher did it for that reason), it's just that Christopher is a writer who is getting more and more detailed and therefore takes time to develop all aspects of the story, which I find admirable actually. =/ And then there was the last part that he had to make up for which was, of course, having Zar'roc stolen. If he would have given Eragon just some random weapon to use then that's another facepalm right there lol. Though like I said, I found Brisingr to be a very good read, but it was more of a bridge or a build-up book, if you will, more than anything.
Anyway, I think it will be well worth the wait. As I said, Paolini is an extremely detailed writer which is why I don't mind the wait for this book. There's no possible way that he can mess up the story now with so much build-up behind it coming from Brisingr. It's going to be excellent and well worth the wait no matter what. And I'm honestly expecting roughly a thousand pages, no exaggeration involved. =/