I wanted to briefly highlight my CP experience. I recently had my CP interview at a US Embassy in the Middle East. My immigrant visa (green card) got approved and here is a brief outline of how it went.
I came into the Embassy and submitted my documents to the Immigrant Visa section. The employee had a checklist of documents and went through each one asking me for the original and a copy. This was not the interview but just the submission of documents phase. The consular who would interview me would show up at a different window later. Here is the list of the documents I submitted/they asked for:
1 recent photograph 5x5 cm, white background
Original Passport + Copy
Original Birth Certificate + Copy
He then asked if I had an Affidavit (I-134) from the US and I did, so I gave him the original
Work experience letters/Offer of employment (I was currently a student in the US and also working as part of the degree so I had this)
Bank Statement + Copy
High School Diploma + Copies
University and Advanced Degrees/Transcripts + Copies
Police Certificates from all countries where I resided for more than 6 months since reaching the age of 16 + Copies
Selective Service Notice + Copy
After collecting all the documents (original and copies) he asked me to go pay the fee after which I'll be called for the interview.
I went to another window, paid the $755 fee and then had a seat. Waited about 30 mins after which I was called to another window.
She was very nice. I came to the window and told her I had additional documents (such as references, letters, etc) she looked at me and smiled and said she didn't need anything else. She made a comment about my educational qualifications and smiled again. At that point it was clear that my green card was already approved and that this wasn't really going to be an interview. So I just chatted with her about when she got moved to this Embassy and where in the States she was from. I then told her I'd been to that State and we went on to have some small talk about touristic destinations in the US. We then talked about my field of study and I asked her if she liked that topic in high school, we joked around for a bit. The system was running slow so she was a little frustrated at that. In any case, she then asked me to raise my right hand, take an oath affirming my answers (on the form) to be true and then took my fingerprints. She asked me if I had any family in the US, I replied and then told her about my family and where they live. She asked me what motivated me to apply for the lottery and I gave my response. Anyways, then she told me what she had watched on Television the night before (related to our earlier discussion on my field of study). She asked me if I had already done the medical (which I had and they were awaiting the results which should've been the next day) and she said my visa will be ready for pickup in a few days.
That's it. I think my case was unique because of my educational background and qualifications but nevertheless it was very smooth running with no problems. I pick up my passport in a few days and then I'm heading back to the US.
My advice to everyone is to not to try to find short-cuts in the documentation. Give them what they ask for and I know from personal experience some of the documents require a lot of work, patience and effort (e.g. certain police certificates as I found out from my adventurous trips) but they are necessary so get them. If you have all your documents in tact and they see you can support yourself, it isn't a problem. If your case number is high I recommend CP. If your case number is low and you are already in the US, maybe AOS is a better option. I did CP and am quite happy with it and would do exactly that if I had to do it all over again (and I have been living in the US for several years now).
Alright good luck to everyone and thanks for those who assisted myself and others in answering questions. This forum has been very helpful indeed.