I have been working with the Genuino 101 for a few weeks now; and researching the internet for days regarding I2C.
It appears there's a general consensus that the Genuino 101 library is for some reason particularly slower than the more mature boards when using I2C. Compared to the Mega, many people have noted that it is 10x slower in some cases. Please note this is not a hardware issue, I have spent time analyzing the bus and the signals appear to be okay; the delay is definitely in firmware somewhere.
I'm wondering if Arduino will be addressing this issue; and whether anyone has been able to achieve good data rates using I2C on the Genuino / Arduino 101?
Example of documentation of the issue: