While I don't think it's a great solution (give up my vacation time to do more work?!?) I'm surprised so many people think this only plays to the employer's advantage. I've been in a number of interviews where the potential employer has lied through their teeth about what they do and how they do it and even stupidly accepted an offer as a result of one. Going through this process there would've saved me the miserable few months before I had to resign.