[slimfiv]

... and focused more on features that are useful advanced amateurs

I actually don't think this is quite right. I'll quote Gary Adcock's Macworld review:

"Most of the features introduced in FCP X are welcome and badly needed. Some are long overdue. Still, others are positively jarring and require a change in mindset to appreciate."

There is no doubt that Apple made it unusable for high-end pros (for the time being, at least) but I feel they also added many things that high-end pros would have really appreciated, had they been able to use it seriously. So it's not quite as simple as "amatueurs only" (even if you're talking about advanced amateurs.)

[ugh]

That also explains why professionals were going absolutly wild at that National Association Of Broadcasters event where Apple demoed Final Cut Pro X for the first time.

They liked the new features and interface changes they saw, they liked the complete rewrite (64 bit, much faster, background rendering) and, most importantly, they didn't know which features would be missing.