I'm not positive about this, but...I think this card might be better than Neural Katana.
Why do I say that? Well, they're basically the same card. A cheap cost, medium-strength sentry with one subroutine that does a handful of net damage if it fires.
What's different? To start with, Cortex Lock is two credits cheaper. A turn-one Katana could be devastating to the runner's grip, but unless you had a Hedge Fund in your opening hand, rezzing it will leave you almost completely broke, giving the runner ample opportunity to recover. On the other hand, a install-install-take credit opening followed by rezzing Cortex Lock leaves you with enough money to threaten a Snare!.
Another difference is that Cortex Lock is strength 4, not strength 3. Meaning that it is out of easy Mimic range. This is huge--most runners have been using Mimic as their insurance policy against facechecking early ice, and it does nothing against Cortex Lock until they get their Datasuckers online. It's also just a tiny bit more taxing for some killers, although Ninja, Dagger, Switchblade and Alias are equally effective against both.
The last bit is the key, doing damage based on unused MU. Obviously, builds revolving around Sage, Overmind, Ekomind, and/or Data Folding hate this, especially out of Chaos Theory. But it's still dangerous in other matchups. The old adage "run early, run often" means runners will make some of their early runs with only one or two MU used, letting you dish out two or three net damage on the first go.
It does get substantially weaker late game, and seeing this card out, a careful runner will set themselves up to exactly their memory limit, letting them waltz through unharmed. But most runners hate net damage, and if they have even a single unused MU they will pay to break either this or NK, and with the additional strength that this provides that will be slightly more difficult.
I think that decks which have long since abandoned Neural Katana due to Mimic-related woes will give Cortex Lock a serious thought, and Sage/Overmind decks will go into their matchups afraid of this card.