I did this to my 987 gen 1. - see profile photo.
Definitely needs alignment, but I'd certainly recommend the springs. There's a noticeable change to the body roll on track and the stance is much better if you have a non-PASM car, since that left the factory 20mm higher than the PASM cars.
One word of warning though - you may find yourself replacing other suspension components shortly afterwards. In my case, all 4 drop links needed replacing after about 500 miles. This is mostly because all the lower suspension parts are now sitting in a different position with the car lowered. In the case of the drop links, this means the rubber bushes are getting worn differently and ultimately if they were near the end of life, they just fail much faster.
I also ended up replacing both front dampers about 1000 miles after putting the springs on - one had collapsed completely. Hard to say whether that was related or not, but again the damper is operating in a different range so I wouldn't be surprised if that accelerated the wear rate on an old damper.
All in, the springs are a cheap and worthwhile upgrade, but the drop links all had to be cut off which was over 4 hours labour plus parts so I ended up spending quite a lot more than planned.
Had I done it all at once, it wouldn't have been a huge leap to just go for full coil-overs considering how the costs added up.
For what it's worth though, if I went out today and bought another new (used) 987 S, I'd drive it straight to Zentrum and have them put lowering springs and a diff in it before I ever used it. In my opinion they are the two best upgrades you can do to this car.
