Yes it is the real deal. Alot of advertisers look at that ranking as well. I have been working on my ranking since I started this blog a month ago. I started at 12million and I am down to 2.2million already. =)
Alexa Ranking is based on your website traffic. That's why they call it Alexa Traffic Rank. If you have many visitors coming to your website everyday you will get traffic rank so high. As of now my website only getting 150+ visitors/day and my alexa traffic rank is "400,100"
I haven't put up Alexa Ranking in my blog but I have visited the site. When I checked my blog's rank, there was a big difference in terms of number of visits compared to what I already have at my blog. It surprised me because I don't know which one is more reliable. And that enormous number of visits is so unbelievable! That's how I feel.