I can confirm that, been looping a 2K 4K video for 15 minutes on my i3 and no noise yet. Silent, fanless, no fan, no noise, I even try to put my ear next to it. True for other cases as well, I only have the fan run when I set up the SP3 for the first time (updating, etc) or graphically intensive games like Asphalt 8 and desktop games.
For those of you interested, I was looping [Ultra HD 4K] STAR WARS 7 Official Trailer, downloaded with IDM in 4K quality (yup, 4K, not 2K not 1080p), and played with the latest version of XBOX Video app.
For 1080p, I have watched the entire "Earth to Echo" movie (the movie in the SP3 presentation when Panos was demonstrating the front facing speakers) without the fan running at all. Now go return your i5!
I am now looping the same 4K video with both the XBOX Video app and PressPlay Video app side-by-side. Its been 20 minutes, and its still silent. It gets warm though. It boils down to either the i3 is impossibly efficient, or my SP3 actually has Core M in it.
I find the i5 fan noise annoying. To me it's very noticeable from ~3 ft away and honestly is one more of those things why I am now, after having had the SP3 for a couple of weeks, leaning more and more toward that it's not a viable laptop replacement. When my laptop is docked and located on the same spot on my desk it never makes any noise. This is in an office environment, email, MS Office, web browser, RDP, and light misc app usage.
Don't know whether it's exaggerated, but to me it's annoying as hell and I am unlikely to put up with it.