Well after about 10 months passing since I received the Kartboy shifter bushings I finally installed them. Install was relatively easy, the biggest issue was dealing with tight quarters. I did this with ramps, and I felt a little cramped underneath the car. I did end up with the slight gap on the driver's side of the main shifter bushing, and this is normal as per Kartboy's directions, common on WRX's and apparently nothing to worry about.
The write-ups already on line cover all the bases, and this is really a quick, easy mod. If you only want to go under the car once and not have to crawl out when you realize you need a 13mm socket for the new Kartboy supplied bolts for the rear bushing, bring the 13mm socket with you. I'm sure only the lowest of the low profile torque wrenches will access the bolts, so ensure you don't over/under tighten if yours doesn't fit. Cross-members are a non-issue on the WRX.
Shifting is much, much more positive and shifting gears seems much more smooth, and definitely much more enjoyable. It's amazing how soft, like gummy bear soft, the OEM bushings are compared to the KB's.