The biggest problem for a yo-yo trickster is that the [fixed axle] yo-yo may not snap back well when he wants it to because it's lost its spin momentum. All kinds of things are done to change the moment of inertia and reduce this loss of spin while it's in sleep mode.
Apparently, the thing is amazing. It can sleep for a hideous amount of time (like on the order of 10-15 full seconds) and still snap back at about the same speed as a fixed axle that's made to come back almost right away.
This isn't the same as the Yomega Brain. That one has a clutch mechanism that releases and grips depending on the speed of the spin. But it will always grip if the yo-yo gets too slow and it will only release when it's fast enough. It's a "Yo-Yo For Dummies"... like Automatic Transmission. But a serious yo-yo trickster needs a lot more control over the throw-sleep-catch sequences.
My only comment was, "I'll get you a pack of cigarettes on my way back from lunch" >KD