Hi-Sec Auto Tracking: +1 range on bunkers, turrets, and drones Neosteel Frame: +2 bunker space, more slots for scv in CC and fortress Building Armor: +2 armor on all buildings Has any terran player used these upgrades with any regularity? The only one I've used often is the Auto Tracking, but mostly for turret range. I can see these being useful for guarding expos or a shared choke in 2v2 maps, but not sure if the cost for upgrades provides enough rewards. On an unrelated note, the bunker looks pretty sweet when you get the Frame upgrade.
I use building armor if I'm planning on an FE planetary fortress against Zerg. It makes it fairly invincible against Banelings.
This may be a noob copper strat, but i'm #1 copper and do fairly well against guys who are top of bronze so i'll chime in. On maps or battles that you will have a massive surplus of minerals i tend to float a command center to islands and line them up with anti air. Basically they scam and see your base there and send ships and get raped. This buys you a TON of time to get your vikings or what not to help defend and the +1 range +2 armor AFAIK will keep them alive a lot longer. Being as you have a ton of minerals and are pressed to spend them all with the amount of mules you can make i dont really see this as wasteful as the only times i've ever lost on these maps was when i was out of gas.