I don't diss Idol, but I wouldn't want to go on it to start a career...
It IS designed to be a money making machine for 15 mins, and then its time to move on to the next series. There may be some serious vocal talent on there, but the chances of there being some seriously good songwriting talent - I don't know. If they were into the songwriting side of things, I doubt they'd go on a competition where your album is written for you if you win.