While I didn't expect there to be an "HD Powerbook" or that Tiger would have a resolution independent UI (it's a nice idea, but would be very hard to do well) I came across an image on Apple's PR site that shows off just what this "resolution independence" is, and also why it's not in Tiger.
The image is
here. (1.7mb jpg) I'm not embedding it due to its size.
Now this image is a strange resolution (2112x1600) but it'll have to do for this example.
As you can see, on first impressions, everything looks huge on it. However, imagine that instead of viewing it on the 100ppi screen you're likely to be using currently, you're viewing it on a 12" Powerbook running at 2112x1600 native resolution. This "squashes" everything down in physical size, and effectively leaves you with the same workspace you would have on a 1024x768 screen.
However, because there are so many more pixels being rendered, everything onscreen is much sharper, clearer, and less pixellated when compared to a powerbook with a 1024x768 native screen.
While this looks better, and sharper, there are also problems caused by it. For simplicity's sake, lets say that this new screen is running at 200ppi (pixels per inch) instead of the old 100ppi. This means that older applications that weren't designed with resolution independance in mind, will look a quarter the size they should onscreen, which is far too small, and would be unreadable.
Having a resolution independant UI will also give you more flexibility though. If you're able to have your UI running at the recommended 200ppi, you could also have the os render everything at 150ppi sizes, for example. This wouldn't be a good idea if you're reading a lot of text, but depending on what you're doing, it may be a good idea, as it will give you more working space on the same screen as it makes everything appear smaller onscreen.
This image is a good example of why I don't think we'll see resolution independance for quite some time though: if you look at the spotlight menu, the input box is horribly pixellated (blocky) around the edges, as are the icons in the results menu. This is because these elements are designed for 100ppi, and are not resolution independent, so they have to be stretched to 200ppi, which is why they're so ugly.
However, this is also adding another problem. Rather than working the graphics card at 1024x768, it's now running at 2112x1600, which will put a bigger strain on the system, meaning that performance will be worse, or more powerful machines will be needed.
Yes, it may be a reasonable extra resolution on a small screen like that, but imagine 200ppi 23" screens. Rather than running at 1920x1200, they would run at (roughly) 3840x2400!
So while it's nice to dream about resolution independance, and higher resolution displays on the Powerbooks, I can't see it happening for a long time yet. Yes, there are Windows-based laptops that run 1920x1200 on smaller screens, but Windows is far from supporting this well at all. It can handle the font scaling
reasonably well, but practically everything else in the OS ends up looking like crap. If you choose not to change it, then everything is far too small to read clearly.
Currently, I believe Apple have made the right decision to go with 100ppi on most of their screens. It's the perfect balance between workspace, and clarity for reading.
Note: my figures may not add up correctly, but you should be able to get the general idea of how it's supposed to work from this. (it is 3:15 am now here, so I'm not thinking entirely clearly)
