They said it will beone book a season, which is pretty damn good; the main problem will come around season three, because 1. DWD is nto finished, and 2. it follows the exact time path Feast for Crows does (as in it doesn't take place before or after, but during). When he finishes it those two books alone will be able to make another 2 seasons.
I only have hope because GRRM has written about 130 pages this month alone so far, and has been actually giving updates.
As for HBO, yeah that reputation sucks. At least they admitted that they totally fucked up with Rome - they forgot to add in the dvd sales along with something else so it looked as if they were losing massive amounts of money (shooting in the most expensive location in the world: Italy), and each episode cost a little over one million to make. With the dvd totals added in to the gross profit they realized the mistake way after it was too late.
The good thing for Ice and Fire though is they are shooting in Northern Ireland (so it's a lot cheaper), and they are getting sets from all the epic "ancient" movies like Troy and Kingdom of Heaven, so they can refurbish them to their style at a discount price while still having amazing quality.
This is why I am excited: they cut overhead dramatically, the cast looks amazing, the location is damned spot on for the series, and the books are actually basically being transferred over intact.