I have a manual, but I'll weigh in with my $.02.
I know two Honda guys that trashed their tranny's from doing this. A friend of mine owns an '02 WRX auto and shifts it very hard. I haven't read of anyone destroying their Subaru tranny's this way, but who knows what might happened 50k miles or so later. I do it occasionally on my wife's OB.
One thing I would definitely do is to put some synthetic tranny fluid in there (complete flush, not drain/fill). You might be able to find a little more info by searching in the tranny forum.