I bought a Flirc case for a RP1 two weeks before the RP2 was released. The case had a manufacturing fault and the short screws wouldn't engage. I reported the problem here and I was sent a new case and told to just keep the defective case. I purchased screws 4mm longer than the originals for the defective case giving me a spare case. The RP2 was released so I bought one. Because the CPU of the RP2 wasn't in contact with the Flirc heatsink I attached a small aluminum heatsink and ran in a cheap plastic case. The RP3 was released so I bought one and ran it in the plastic case with a heatsink attached. The two Flirc cases were stored away unused for a year.

I bought some thermal pads and decided to give the Flirc cases a try. I used Parker Chomerics Server-Grade G570 Thermally Conductive Transfer Pad- 20mm x 20mm x 1.78mm In a Flirc with the RP2. Idle temperature improved from 44 degrees to 30 degrees. After installing the RP3 in a Flirc case with 3M-467MP Thermally Conductive Adhesive Transfer Tape - 25mm x 25mm x 2.0mm idle temperature improved from 53 degrees to 37 degrees.

The Flirc improved the RP2 by 14 degrees and improved the RP3 by 16 degrees compared to running in plastic cases with aluminum heatsinks. I was shocked by the improvement.

Edit: For easy removal of the RP3 micro SD card use a utility knife to trim a bit of the plastic base. The trim only takes five minutes and it isn't noticeable.

Edited April 6, 201610 yr by Whiznot

Thanks so much for writing that, I appreciate it. I have a pi3, and was going to do some thermal testing and analysis myself, but I can't get up for air to do this. I'm so busy, it's unbelievable.

I've known that the case was a huge improvement thermally for some time, but without a technical write-up, I'm hesitant to boast this in marketing material.

The reason I've known is Eben (pi founder) has been using the flirc case for pi3 design and bringup for it's thermal performance. Their reason was exactly what you said, it's far better than just a heat sink you stick on. 

Any chance you have a thermal couple? I'm so short for time, I'd very much would not only like to thank you for the detail and analysis, but I would compensate you for taking the time to put together a blog post. PM me if you're interested.