I'm in a similar boat as many of you above. I am working in a great paying job with great benefits in a field that, while interesting, is not what I want to be doing for the rest of my life. I just had my interview yesterday, and if I get in, I will almost certainly take it, but I'm not super happy at the prospect of not having the money that I currently make.
I realize I'm counting my chickens before they hatch, and all I can do is wait and see whether I get in and what (if any) the offer is. Still, it's a tough choice.