Okay..let's face it, being so jacked up you can catch a bullet in your bare hands is kinda cool...however, few realize what the drawbacks of this technology are.
Most dangerous of all are the "flippable" boosts (adrenaline and Sandevastian). Think about the horrid toll the switching takes on the character's body. Think of it as changing gears, but the clutch isn't depressed fully, grinding gears. Also, reflex boosts are like Speed, they accelerate you for a time, then bring you back to a coasting after their effect is turned off, or wears out. The sudden change from normal to hyper-mode is an instantaneous one (it has to be to take effect in approximately three seconds). This constant upshifting and equally rapid down shifting has got to take some kind of a toll on the body, and the mind. Be it anything from addiction, to fatigue, there are going to be obvious side effects of this cyberware. My favorite, that I make sure Trax deals with, is that the usage takes a lot out of him, actually lowering his reflex by 1d6+1+BTM for 1d6 turns (of course the mandatory 1 turn applies). NOTE: The mathematical formula is correct for this computation, as the BTM is a NEGATIVE number, adding it would create the proper effect contrary to subtracting it. It is most realistic, because let's face it, when your adrenaline enters your blood stream when you are fighting, when it wears off you are tired, and maybe even exhausted. Because of these effects, this should help your players to limit the usage to only when REALLY necessary.
A good example of the effects of switchable reflex enhancers is Sarah from Walter Jon Williams' HARDWIRED. Not only did the usage of "Weasel" wear her out (not being able to breath, or at least having trouble doing so, and exerting yourself takes a lot out of you). Also, when she or Cowboy came off their boosts (though Sarah had to use that inhaler to trigger it) the two of them were QUITE out of breath.
Usage of this is not so much for balance, or gameplay (though it definitely influences that). This is mainly for role-playing purposes. Though you should see some of my other articles for that kinda thing.