Intel hasn't given us specific information about the specs and speeds of its first Compute Cards, but you can expect the fastest ones to approach the performance of high-end fanless laptops like Apple's MacBooks.
As impressive a feat as this might appear, at first, one must remember that Apple devices running last year's A9X are already faster than the Apple MacBook running Intel's equivalent processor, according to the latest GeekBench numbers - http://wccftech.com/apple-a9xi.... So, I fully expect that newer devices running Apple's A10 or Qualcomm's Snapdragon 821 (that are slightly larger than a credit card due to some additional features that Intel's compute cards lack, such as a touch screen, gyro, motion, barometric, gps, cdma, gsm, lte, wifi, dsp, hsm, etc.) to already be a lot faster than Intel's fastest Compute Cards (assuming that the MacBook remains the benchmark performance).
I think that what Intel's Compute Cards will have going for them will be accessibility, programability, price and the ease of interfacing them to custom devices for developers... That is what Intel should be emphasizing. Vending machines, signage displays, self service kiosks, home automation hubs, assembly line robots, etc. do not need lots of computing power... but they need reliability, availability and dependability with minimal human intervention in some of the harshest environments, every single day of the year.