I've had pretty limited experience with cryo treating parts, but when I have, it's worked very well. I've had a bunch of problems with my 901 Porsche transmission (very similar to a Hewland Mk 9) and decided to go all out on the latest one. I had Mike cryo treat and REM polish the ring and pinion, all the bearings, and gears 3-5. The price was good and his service was great. He worked my stuff in right away and turned it around faster than I expected.
The great news? The transmission now runs 40-50 degrees cooler! In previous versions of this transmission, I around 150 hours worth of data to show it runs 235-250 when being pushed. The first time out, it ran 180 degrees. Simply amazing. I will now use Mike to treat any transmission work I do and will have any new motor parts done. I have brake rotors that are going to him soon as well!
He's a long time Apexspeed guy and great to work with. I have no interest in it other than being a very, very happy customer.
http://www.cryosciencetechnologies.com/