Just read a post on Car & Driver's forum about a guy with a 07' WRX who complained about the shifting like I do. He said and I read that GL 5 gear oil will corrode and shorten the life of syncros if they are brass or bronze. I had read it will cut it in half, and only used if there is Another reason to use the oil. I wasn't sure the material of the syncros, so was waiting to find out for sure, but he says they are brass, and the trans oil goes into the front differential, and why the GL5 is used, which is good for the diff, but not the trans, and he switched to Redline 75W-90NS. He also said the shifter had a rubbery feel and replaced the bushings with polyurethane ones, and says there is some vibration, but a feel of the trans working.
I don't notice a rubbery feel, but more of a notchiness. Maybe feeling things working would make me feel more in tune with it, but that can wait. Protecting the trans, as long as the diff is also, and smoothing the shifting would be nice.
VF