While you're a it, see if GTM will post here. Might be a nice read for anybody who still has nagging doubts about the gearbox.

No, actually that is not how it works. The syncros were putting in a lot of overtime to keep up with matching the input shaft speed. They simply wore out from the abuse, which they were not designed to take. You can have the same issue in just about any car you do this in. While I'll admit it happened rather quickly on my Z, it was not completely unexpected nor unexplainable.

Hmmm, I posted in a similar thread about this and I have to say it again, skipping gears shouldn't have any adverse effects on your transmission. Maybe, MAYBE, the syncros but not the transmission itself. I have been skipping gears for over the last 9 years in cars from 5spd to 6spd and have never had any issues.

I assume when skip shifting that you are giving the transmission a moment in neutral to let the revs die down. In other words, you're not trying to speed shift a skip shift (fortunately, H patterns make that inherently difficult).

A correct upshift will not wear the synchros at all. You put in the clutch, put the car in neutral, pause (momentarily) for the revs to drop to the level of the next gear, and engage the new gear. With a light flywheel, there is basically no pause. With a heavy flywheel, and a large jump between gear ratios, the pause is longer. When skip shifting, the ratios are further apart, so you pause even longer. If done right, it ends up just being a nice relaxed (but not too relaxed!) shift.

You know you've got it right because the lever should want to slide right into the new gear. You can tell you're using synchros when you have to press on the new gear for a moment before it "lets" you in.

So you're both right: speed shifting and skip shifting together will damage synchros. Gentle skip shifting should never be a problem.

To get back on topic...

The 6 speed gearbox has been able to handle power just fine. A couple of people have had problems with actually breaking gears, but I would not consider that the norm. Those folks(like Alberto) abuse the transmission worse than even the average enthusiast.

However, the stock clutch will not hold up very long at all. In fact, the stock clutch won't hold up at stock levels if you drag race often. The clutch in my 05 lasted ~25k miles, but that included about 150 passes down the 1/4, all with full throttle upshifts and mid-rpm launches.

Also, since the intro of the HR, Nissan has had problems with the integrated slave cylinder within the transmission. Here's a thread on another site that may be of interest:
http://my[remove]350z[remove].com/forum/vq35hr/428616-bad-news-for-hr-owners.html