Out of 27 BP's, I only have two that refuse f/t. One is a female who was imported as an adult and took 1.5 years to eat *anything*. Now she takes live small rats. The male that I purchased with her took just as long to start eating, but he now eats f/t without any hesitation.
The other non-f/t eater is a '94 farmed female that I've had since she was a hatchling. She has always been a live mouse eater. I occasionally try f/t and I think she's gone for it 2-3 ? times ever.
The rest of my guys/girls take f/t without any problem, and I've been sucessfully breeding for 5 years. Patience is definitely the key. I think that's the key to most things BP though. 
Once the snakes accept f/t, as long as the rodents are warmed enough (I test by my hand, if it feels hot but not burning, it's about right) I haven't noticed a whole lot of difference in feeding response.
It does take a little longer than feeding p/k or live, and I definitely have to plan ahead. I'm guessing that could be the biggest factor with a huge collection - with under 50 snakes that isn't too bad, but with 1000 snakes that would be a *huge* time issue.
The only real downside that I've personally found with f/t is sometimes I have leftovers - defrosted rodents that weren't eaten. Fortunately, I have a 5.5' Ornate monitor who acts as a garbage disposal.
Elizabeth