Interviewed a couple weeks ago and got the offer. 7 out of 13 were offered a job. During the interviews on the day prior, 6 of 13 were offered a job. I didn't use an interview prep course but I did study IFR procedures and regulations heavily. Also read all the gouges on aviationinterviews.com to help prepare. Gouges were spot on. Know your current aircraft well. Overall a great experience and well organized. No applicant seemed confused over what was going on. They do a great job putting your mind at ease. Good luck!

Edit: I did purchase and read Checklist of Success by Cheryl Cage. Worth it in my opinion. It was interesting to see the different interview styles/techniques used by the hiring team.