Labor wise is a kick in the nuts. The Alldata labor time guide says 3 hours. An Alignment after is an absolute must.
Usually most people can do them in their driveway in under 2.25hrs with a cork screw spring compressor. Wagons are easier than sedans.
They fit nice in the strut perch on the bottom. The top of the springs don't match the foot print in the top mounts. However, your springs and the STi springs are wound and machined flat at the top so it pretty much doesn't matter how the sit in the top mounts. They will make themselves a new foot print as they settle.
I've had my STi springs on 2 weeks (07 2.5i wagon). They dropped the car a little at first. They have settled in the perches now and dropped a weee bit more now. The ride is pretty excellent. But when you really get into corners it doesn't let the car roll over as much. And switching back is a lot more precise. The car is a ton more controllable. More sporty, without the jarring of lowering springs.