Very friendly, highly recommended.
However, the tech phone screen and tech interview asked basic concepts regardless of background (e.g., "How many bytes in a 64-bit number?"). They were looking for specific answers to get through the screen. The Skype interview (phase 2) was similar.
Be careful when answering; they are looking for specific answers to filter you, not evaluating your ability to answer or explain.
Skype Interview: Asked about memory management, ARC, etc. The interviewer was looking for a specific answer, and I didn't use the keywords. In retrospect, I should have been clearer.
Recommendation: Open a separate window and search for the question, then use keywords from Stack Overflow or similar resources.
The following metrics were computed from 2 interview experiences for the Yelp iOS Developer role in United States.
Yelp's interview process for their iOS Developer roles in the United States is fairly selective, failing a large portion of engineers who go through it.
Candidates reported having very good feelings for Yelp's iOS Developer interview process in United States.