Since we don't have a general discussion thread, I'm just gonna stream of conscious here. These are my general thoughts about 4b. There are going to be spoilers below so read at your own peril.
Weapons: I'm a big fan of the changes to thermal and EM. Thermal weapons are worth picking up now and saving for programmers. EM weapons are no longer the king of looting processors, and spectrum is a fun double-edged sword. It can be really effective against packs of enemies, but it can be dangerous when it happens too close to you.
The new hacks: Trojan(Botnet) is basically a substitute for deep network scanners at the cost of raising the security level. I haven't played around with it too much, but it's very interesting. Trojan(Track) is less handy in my experience. In big factory levels, I don't really care what's going on way behind me. Force(Overload) is very interesting; I imagine this one will be best used to prepare ambushes (have to be careful with it - the first time I used it I hung around and fried myself). I don't really care about Force(Jam) too much, cause if I really want a Garrison disabled I just blow it up. I imagine it'll be a handier hack for stealth/speed builds.
Garrisons as Machines: Great addition. It severely hampers, but doesn't kill, the "use programmers to find the stairs" trick. It also taught me more about the mechanics of the game. I had map with a Garrison right next to a terminal. I tried to hack the terminal and got locked out. A grunt instantly popped out of the garrison to investigate. Although I knew that lockouts cause investigation squads to be dispatched, seeing it happen was quite jarring. I've significantly reduced how many times I'll allow myself to get locked out of a terminal. Another time, I was fighting some grunts in research near a Garrison and a sentry popped out. I imagine that was a Reinforcement squad. Seeing it happen up close helps you understand the game mechanics better.
Garrison as a map: Hooboy. High risk/reward indeed. I'm not sure how to incorporate them into a run to reliably get a benefit (besides the hack). As K said, you gotta be beefy just to go in there with a good chance of making it out. I really like that this is a new way to get allies without mucking around with fabricating. My tentative view on Garrisons is that if I've in a factory or research level, I haven't been on the level too long, and I'm in good shape, go in. There's a chance of going straight to the next level which is worth it. If you've already been on the level for awhile, chances are the exit is close so it's probably not worth it (and you're probably overdue for a drop in the security level, which the Garrison will certainly not do).
Unrelated thoughts on Alpha 5: Two of my runs in the last week ended on -2. In both runs, I artificially kept my inventory low. During the tournament, I usually had an inventory of 20-40. This time I intentionally limited myself to around 15. It really, really, really made things harder. My second run probably would have won if I had my full inventory, as opposed to leaving caches half looted. If changes are going to happen to push back against the huge inventory meta, I think they need to be balanced with 1) a further reduction of cogmind Armor to crit vulnerablity (you lose armor so fast, jesus) and 2) quality of life improvements to fabrication to make this easier and less tedious.
Finally, is Armory a new thing? In the tournament I never found it. My last 3 runs now have found the (locked) entrance to the Armory.