1) Icons is a HUGE task. There's a demand for as many icons as possible, especially file type icons as a criteria for a successful pack. And in particular for premium suites. A minimum pack would contain about 50 icons. And then you'd have no file type icons. If we add some standard file type icons, a typical IP would contain 110-120 icons at least. To make these look good, I do them at 512x512 px and scale them down to match the new Vista size. This makes the detail level rich, but it's a lot of work. You could easily spend hours on a single icon, and you have at least 50 to do. It's not impossible, it's just a huge task for beginners (and veterans too), unless they've made up their mind about it and are prepared to put in many many hours of work.

2) I use iTunes myself and never dared skinning any media player except WA 2.x. All that xml scares me away as codes are pure gibberish to me. No matter how many times I sit down and try to learn a little I just get more confused.

3) Sure there's a lot of elements to skin, but pulling of a WB isn't as hard as it might seem. To make it look as good or better than Vista Aero, as you say, is simply a matter of the talent of the person behind the skin, and personal preference of the person who uses the skin. If I didn't have a job and other obligations, I could probably roll out a pretty good looking wb in a week.

I think the amount of work and time involved in creating skins, might hold some people back. There's a lot of knowledge to it too, gotta know how to use PS i.e., if you're doing media players, you're gonna know how to code them or have someone to do that for you. If you do know these things, skinning itself isn't so hard getting into, there's some experience involved for sure and you gotta invest a lot of time too.

A good thing is collaboration, people can learn from each other, do each their part of a suite, if that's what they're doing, knowledge will be shared that way, plus they can encourage each other.

patrick24, I don't want to give it away to soon, but this has been in the works, from GUI Magic, for the past two months. Nothing finalized yet, still have a few kinks to work out.
Forgot to mention, as of now (this may change later), it will be call B.Y.O.B. Build Your Own Blinds.

To me skinning (as others have touched on) isn't harder, just more time consuming.
Back in the day, you could do a WB in 3 or 4 hours. Now it takes 3 or 4 weeks. Big difference.
Same goes for Iconpacks. 100% more detail is involved now, also.

Looks like that one is confiscated already...