The interview process involved a phone conversation with the hiring manager, followed by a Skype interview with the engineering team. Both of these were a fairly standard vanilla mix of technical plus "soft" questions.
Then there was a project, which I was given three days to complete. This was a moderately challenging project involving relevant technology, some of which was new to me. I turned in the project, then received absolutely no feedback whatsoever. I was told I would receive an Amazon gift card as compensation, even if I was not hired. They did honor that, but it would have been nice to know what I did wrong or why they didn't hire me. My project was functional and completed the objectives set forth, but admittedly may not have used the best solution. However, no feedback was provided to me other than "Thank you for your time". I even followed up with the hiring manager, but my inquiries went into a black hole.
Job offer or not, it's professional courtesy to give some level of feedback to an applicant. I would have been fine with hearing, "Sorry, but your skills just aren't up to what we're looking for." As it was, I was left feeling confused and ultimately relieved I didn't get hired by such an unprofessional organization.