level 3 base (as in, not even Alphaware) Cerebral Booster rating 3 is only .6 essence. Heck, do it at alphaware for

60k, and you can eve nsqueeze in a Control Rig. That gives you three extra dice at the cost of one for the lowered resonance, which can be earned back. I still, personally, don't really get the whole 'cyber detracts from resonance', but whatever. It seems like a very good idea for the logically minded technomancers.
But as I understand it, you can't write a program over rating 6. The catch is that on pg 240, creating your own code, it shows costs for up to rating 6, and the threshold on extended tests, but it doesn't specifically state one way or the other.
Now, back on pg 225 , it says "some cutting edge or miliraty can rank higher" , although it never actually states the top end, assuming that there is one. Now, this is kinda important information to have. For one, because a program can't run on a system with a lower rating. So if there's a rating 7 program out there, it stands to reason that there are rating 7 systems. or higher. Now, if you're going to try running S-K Prime , that kind of thing is important information.
I suppose that this is the kind of stuff that may be covered in the new MAtrix book, but with only slight rewording, they could have given us all of that to start with.
In the mean time, as it's written, an experienced technomancer can beat FastJack. Jack's programs can only go up to 6 (so far), and his logic is of course limited. Where the technomancer has the same skill rating limit, the same logic limit, but can blow him away with programs, through a high resonance and threading, or seriosly tough complex forms. And that just ain't right.