After being amazed at how silent the 2015 13" MBP most of the time I eventually downloaded "MacsFanControl" to check if there was any idling fan activity or if it was totally still. this seems to confirm the fans are off most of the time not idling -> It would be interesting if someone with the 2015 15" could do the same test to see if the fans reduce to zero also. It is so great being able to run a computer in total silence. but what can you do before the fans kick in? So far I've been able to; *run a 4K video on a 42" external 4K display through hdmi *run as many tabs and pages as I like *run logic pro with multiple tracks *stream 1080p youtube videos fullscreen on 42 external display *play several basic games such as Jedi Knight 2, dungeon hunter, reckless racing Each of these things are possible with no fans kicking in, in silent operation - which is amazing to me coming from a 2010 MBP where the fan was ramping up for youtube videos and flash content on web pages Well I would have been very interested in this info before buying so if anyone hates fan noise and was thinking of a RMB to avoid it, the 13" pro 2015 can do everything the RMB can in the same silence, but also can do more powerful things with the additions of some fan noise kicking in eventually.