I have seen a few times where someone is clearly shifting too aggressively, or speed shifting or whatever you want to call it, and basically forcing the synchronizers in a manual transmission to work faster than they are capable of. The shift fork that pushes the synchronizer can get damaged or the synchronizer itself can crack. You should really allow an extra fraction of a second to let it engage naturally. You'd be surprised how much leverage multiplication the shifter has on the forks and synchronizers. The STI has stronger components in the manual transmission but a WRX is more of a daily driver and it is irritating when some entitlist yonger dude is beating us up for new clutches and transmission parts under warranty. I think its just an education thing. You can't shift like a maniac and you can't expect that factory clutch to hold an extra 50+ horse power. When you hop in a brand new WRX, the clutch is super easy and forgiving because it's not high performance like an STI. It is a daily driver with probably too much boost for it's own good in my opinion.