Incredibly unprofessional. When the recruiter called, he was very excited and couldn't wait to schedule a phone interview. When the time came, I was ready for the phone interview, but it had to be postponed due to scheduling conflicts (on their end). And then... there was absolutely no further communication from them. They just stopped responding to emails or calls. Despite them expressing strong interest, suddenly they just stopped answering.
Honestly though, I feel like I dodged a bullet. If a company is going to be this unprofessional in their communication, I don't think I want to work for them.