Hands down, the most unprofessional interview experience I've ever been through in my entire life.
I was scheduled to take a developer challenge from 6-8pm. They didn't send me instructions until 7pm after I emailed them and claimed that the delayed start was a way to "gauge interest" and that they usually get emails from candidates right after the start period. They totally wasted my time and energy.
Regretfully, I started the challenge, but some of the instructions were unclear and I was unable to finish. I provided feedback and they defensively claimed "no one else has had similar problems."
I withdrew my application then and there as they didn't strike me as the type of people or the type of organization I would ever want to work for.