Coke,
What apps would you consider the best that you have seen so far?
From the one's I've used, it's USA Today, Bing Weather (so far the best designed weather app), Cocktail Flow (being the BEST one), Cookbook, Movie Guide, Skype, and SkyDrive (ok example).
I would say that Xbox Music is nicely designed, but it's not. Honestly, the Zune software's UI could had been used for some it. For example, the music library (or collection) screen filtered by artists would had been perfect; you can scroll through on the left side through your artists, scroll through albums by artist in the center, and scroll through songs by artist on the right side. And it would had been better to put in better filtering. The main panorama screen can be kept in Xbox Music, but making it a little more....metro. Some of the UI controls can be taken down a notch as it isn't too difficult to tap or click on them. A better Now Playing visualizer should be used, like Zune's. There just isn't enough of the digital motion, or animation, to Xbox Music like there is with Zune. They're usually subtle and here and there, but it makes the user experience better, at least to me. Xbox Music doesn't offer that. At least YET.
OH! I just remembered, the Tom's Hardware and Guide apps. They're nice, but not totally giving the feeling of immersion. I'd like to see some more full fleshed content mostly. A good way to organize would to break up the different subcategories into a main panorama, where the most recent content is show. Kind of like the way USA Today does it, but different, it would show more per section. I wonder how it would look like too if the different sections of the panorama had photo backgrounds. For example, the Reviews section would have an image from each review article, like an AMD Radeon 7870 review would have that as a relevant image, and those different images would be in a mosaic. The best example I can give is on The Verge's website, where they have the day's top articles and posts in a colored hue mosaic.
If I were to design an app in general, I'd use system accent colors, kind of like how Windows Phone does it. Windows Phone apps that use the system accent color give the overall feeling of everything being integrated. Third party apps feel like native first party ones and such. Windows 8 needs to have some of that I believe.