Anyway, just finished Specials. Unfortunately Extras isn't on the Kindle store so I don't have it yet. From the preview chapter I've read it seems to be a seperate story (correct me if I'm wrong) so I think I can safely talk about the Uglies series.
So, the big questions:
Is it good?
Yes!
Is it as good as Leviathan?
No!
Why?
The structure of Leviathan was simpler and more powerful than Uglies. Leviathan held the ending 'goal' constant through the whole series (Alek's ascent to the throne and stopping the war), but also spent the whole time secretly building and making Alek realise another 'goal' (Alek and Deryn being in love, Alek's realisation about his destiny in the Tokyo scene is a great example). Then it brought the new goal and the old goal together at the climax (think 'smoke bomb', 'Tesla' and 'walking stick') and let the new goal compeletely take over in a sudden epiphany for the final chapter ("meteoric!") (Now that I look back I realise this was mostly the structure for Alek in Goliath, I consider Leviathan to be setup and Behemoth to be more about Deryn). I remember when I read the final chapter I didn't expect Alek's decision until the very line it happened; I thought he would simply have to leave Deryn with a dissapointing ending. My mind was blank with the raw emotion that the ending conjured up.
The first book of Uglies was handling this very well for a while, but after a while the story had to move away from this structure in order to continue, and it got very complicated. The ending wasn't a surprise realisation because I had no idea what Tally's ambition was leading up to it. That's not to say it wasn't powerful, just that it wasn't supported by the entire series like Leviathan.
Put simply, compared to Leviathan's intelligently and powerfully structured story, Uglies often felt like a sequence of random events, like Westerfeld was making it up as he wrote.
That's not to say that Uglies is bad, it certainly kept me engaged. In fact you can probabely taste the sheer joy I felt when writing about Leviathan, and you'll realise I mostly just want to reinforce that Leviathan is pure dead brilliant.