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golemslord, I was in the same boat as you when I first got my BRZ. I wanted to drop it about an inch, so I bought the Swift Sport springs and had them installed along with rear lower control arms (necessary for rear camber adjustment), front camber bolts, and got an alignment.
They were exactly what I was looking for. Mild drop, ride quality wasn't harsh, less body roll in corners - seemed pretty planted when taking turns. They seemed to perform just as well as stock...until I did some canyon driving and hit bumps and uneven pavement mid-turn. I first got the sense that the rear end was more 'floaty' than before when I hit a dip on the freeway going at around 70mph before I went to the canyons. The rear end wiggled and felt unsettled, and didn't inspire confidence.
Up in the canyons, every time I encountered mid-curve dips, the rear end wallowed and felt unsettled. I wasn't happy with the way it felt.
So, after some research on here, I went with the Tein Flex Z coilovers. One of the best decisions I made. Now I tell everyone who has the similar needs that I have, to skip the lowering springs and just go to something like the Tein Flex Z's if they're on a budget like me; you're not spending that much more, and you do get more for what you spend.
With the adjustable coilvers, you also get the ability to adjust ride height (which you can't with just lowering springs), corner balance, and vary the damping depending on the road condition. I typically drive it on 'soft' for daily street driving, but firm it up in the canyons and smoother roads. It now feels like I had expected it to feel. Much more stable and predictable in uneven corners, with a better (adjustable) ride quality than the lowering springs + stock dampers.
So for me, who doesn't track the car and only does occasional spirited canyon runs, the stock dampers + lowering springs didn't cut it. And I don't think I'm even that picky.