my take from experience and research (friends, internet, hazy dreams ....): Fem seeds are not good. There are a few methods to creating fem seeds - the above mentioned; giberilic acid and light manipulation are the methods I'm familiar with. you cannot Fem all strains because the trait is in the genes and a lot of IBL strains do not have the trait.
nature does not like hermaphrodites, they are freaks of nature. the female plant is forced (raped!!) into producing some pollen pods to pollinate the same female (doesn't this just SOUND wrong?!?!). said seeds have a tendancy to be female, but there is no guarantee. you could get a male. you could also get hermies.
hermaphrodism is also a result of stress and a strain that was grown from Fem seeds is more likely to hermie in a light stress (light as in light/medium/heavy) situation than a standard seed of the same strain. (eg: Blueberry regular and Blueberry Femenized - 1 day of light stress (as in actual lights, accidentally turned on for 24hrs for one day) made the Fem girls hermie, whereas the regulars were fine)
this is one of the best articles I've seen on the subject of getting more females from regular seeds.
http://www.1stmarijuanagrowerspage.com/how-to-improve-female-male-ratio-of-cannabis-plant.html
if only growing a few out in one grow, a few hermie flowers aren't a big deal as they usually show later in flowering, too late to pollinate before harvest. but a staggered grow getting poppers will screw the younger generation.
my 2 cents on it