I've seen a lot of people talking about it, and I thought I might put down whatever this brings to mind.
1) Am I jealous? In a ... distant sort of way, yes. I'd love to have that much money per book. Heck, I'd love to have a TENTH that much money per book. But to me, it's about like hearing about someone I know win the lottery, except in this case the lottery also included someone who did a lot of work to get where they were. There IS still luck involved, make no mistake about it; if there was a clear FORMULA for getting popular enough to be a bestselling author with a powerful backlist, all published authors would be just like Scalzi -- any new prospective author would be taught the formula so that the company could make money, and so that the company would never, ever, take a bath on some apparent up-and-comer. I wish I had his deal, yes. But I also wish I had that much money just from any source, so I'm mostly just "it'd be nice not to have to do a day job".
2) Does he deserve it? Damn tootin' he does. He's done a lot of work to get where he is. He's gained a lot of followers by providing them with consistent, well-presented, interesting articles and building up an audience even before he became an SF author. He continues to do this regularly. He supports other authors -- not the least of them being yours truly -- by providing a forum where they can possibly benefit from his own popularity. He's written a lot of books, and demonstrated that his books sell, sell well, and sell for a long period of time. He's paid his dues to the field, he's demonstrated his endurance and professionalism, and he's EXACTLY the kind of author any publisher wants on their release schedule, someone who'll sell well to start, and keep on bringing in the dollars later.
Monetarily, the deal certainly makes him comfortable, but even large as it is, it's nothing compared to the really big guns like King or, gods above, Rowling at her peak, where millions of dollars PER BOOK isn't unusual. He's also self-employed, which means that there's a much larger bite coming out of those payments than us wage slaves see coming out of our paychecks. It's not like he'll be out buying private jets and yachts any time soon, unless his OTHER income streams make him a lot more money.
Just by comparison, the largest advance I've personally gotten on any book (as opposed to advances I've gotten in company with Eric Flint) has been $8,000. This pretty much tells you where my book sales sit compared to other authors. In a good year, I might get ~$20k total from advances and royalties. There's a reason I have to write only in time I can squeeze out of other things.
But unlike Scalzi, I'm a *TERRIBLE* self-promoter. I don't like doing it, when not in a group of people who already know me well. I also don't have the time, skills, or effort to spare to make tons of content, to drive traffic to my site, and so on. I don't have the spare cash, most of the time, to PAY people to do some of the things I'd like to do, either.
I ALSO don't like arguing and controversy, for the most part. This is one area where Scalzi and people like Correia have a fair amount in common: they don't mind not only stating their opinions, but doing so on large public forums where they will drive furious discussion, and often very heated discussion going straight to flamewars. This tends to attract readers. I can't do it that way for a couple of reasons -- first, because I've gotten tired of that kind of thing after, oh, 30+ years of flamewars online, and second, I no longer have the certainty to have such slam-bang arguments. I may believe strongly that X is true, but I can't be CERTAIN -- in anything other than the most trivial arguments -- that I'm right. In moral/political arguments this is a strong enough uncertainty that I generally dislike doing more than stating my opinion and then mostly dropping it.
If you want the kind of deal Scalzi got? Well, you'll need luck. You'll also need a willingness to push yourself somewhere, a technique to get yourself looked at by increasingly large numbers of people, and the ability to regularly and consistently sell far, far more books than needed to earn out whatever advances you're given. Do that for a decade or so, and you too could get a big book deal!