I'll be honest, y'all lost me on the Foundation. I intensely dislike the "new" concept of a mystical Matrix; I can get behind resonance being an x-factor much like magic, but basing the entire worlds digital infrastructure on something that not even the designers seem to understand is something I just can't get behind. To me, it feels like a cop-out, especially since the technology of Shadowrun has always been very grounded in what might be possible. Data Trails takes the Foundation a step too far for me, personally, because I can no longer associate a sense of realism with the Matrix, unlike in previous editions where the Matrix was always the evolution of our very own internet and was (largely) based on actual computing principles. As someone who has always appreciate the level of detail invested in Shadowrun, perhaps in spite of consequences like the relatively steep learning curve for all things Matrix, this is not a direction I am fond of.
That being said, I do appreciate the efforts by the writing team on a lot of the actual rules; if I just choose to ignore that whole "no one really knows how the Matrix works" aspect that I strongly dislike, the rules for deep dives seem very promising, and I really appreciate the clarification on Patrol IC. While I felt the section on commlink gear was somewhat underwhelming (especially the fact that there was little love for riggers and their RCCs, which can run cyberprograms but can't accept cyberdeck modules?), the last section on Mastering the Matrix was absolutely fabulous in terms of summarizing the Matrix 3.0 concepts and making them easier to understand and implement in an adventure.
Finally, though, I'm saddened to see the continuation of a trend I've noticed where more advanced rules from previous editions no longer make the cut in the 5th Edition core books.
First weapon modifications were mostly omitted from Run Faster (potentially, and this is all speculation on my part, in favour of demo rules that I don't personally know anyone really wanted and/or are using much), then the rules for advanced interaction with the Astral realms, extended information and rules on initiation, and rules for spell design from Street Magic didn't make it into Street Grimoire, and now finally Data Trails has no trace of the advanced software rules, no technomancer streams or paragons (though this may be addressed in a PDF book I personally think this is a poor choice of strategy deviating from SR4), or all the nifty simsense gear from Unwired, just to name a few.
All in all, I feel that the core supplements for 5th Edition have been solid offerings in the grand scheme of expanding the basic rules for SR5, but as someone who enjoyed playing 2nd Edition and immersing myself in 3rd and 4th I think the potential these books had to be so much more was a sorely missed opportunity.
For what it's worth, I'll keep buying the books as long as you keep writing them, and I want to make sure to note that I don't have anything against the writers here at all. I just really hope the direction for the entire line gets taken a good, hard, long look at, because I personally feel streamlining the play experience is starting to cut into the vastly rich and complex setting I've come to love (and sometimes hate, I'll be the first to admit) over the years.
/rant