My VISA experience might not be much of a help because it lasted for just about 30-40 seconds, but I do have something to share.
I feel all this VISA interview hype has been created by the so called VISA counselors, because it is their business. I was anxious about my VISA thing, so I decided to visit a counselor. And he made it sound so very complicated. He was like....he'll guide me in filling up the DS forms because a slight mistake in the DS forms would mean an outright denial...and that I'd have to take at least a 4 day leave to prepare for the interview..and I need to have liquid cash for both the years or I need to get a loan approval to show readily available funds for the 2nd year( Later on I came to know that he lends you cash if you are short on it

) . It kept me worried for a couple of days and then I decided to go for it myself. I backed myself, and went for the interview...I was confident that there is no reason that I should be worried, because I had with me all the documents that are mentioned at the 'VFS' website.
And my interview(24th June 9:15 AM):
VO: So, You are going to UCI?
Me: Yes
VO: Could I see your offer letter please?
...While looking at the offer letter, he asks: do you have funds?
Me: yes
VO: Your VISA is approved, it'd be mailed to you within a week.
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That's about it. And all the other guys heading to UCI who've had their VISA interviews have had similar experiences...So, I seriously believe that it is just the hype created by these counselors..and nothing more....Just be confident and keep a smile on your face.!!