SoT to me is one of those cards, that on paper, makes quite a bit of sense. You have XYZ cards that are integral to your strategy and getting to play them extra times is gravy. However, in practice, there are countless times that I sit around with it in hand or installed waiting to turn on. I think it has trended down to 1-2 copies from the ubiquitous 3x include for many decks, especially with decks like NEH forcing runners to get faster and faster.
Going back to my "on paper" theory, there are a lot of events you don't really want 3 of in the deck, but you want to be able to play it like you did have 3, that sometimes it feels like adding a SoT in place of that 2nd or 3rd copy makes a lot of sense. And in practice, sometimes that is the case, other times, it winds up just increasing your variance and sticking you with a useless card for the first half of the game.
Out of shaper, it really helps with Test Run/Scavenge, (as well as QT/Freelance Coding Contract if you're playing those), but both of those cards have versatility outside of the combo, making the SoT provide quite a bit playmaking ability while providing stability to your program fetch. And that's the core of what I look for with SoT--is something it does outside of spamming the same event repeatedly. Constantly threatening every event in the heap is brutal, I can protect against AS spam, but when i threatens an indexing, inside job, test run, AND account siphon, the SoT is a window closing machine.